ABSTRACT. Algorithms for coverage control, vehicle routing, and stochastic surveillance have been designed by engineers to enable efficient robotic coordination.  Clearly and remarkably, these problems are exactly analogous to how animals partition a territory, move to exploit resources, move to avoid detection, and search for preys. This talk will review some optimization and design problems for autonomous systems and will highlight some existing (and perhaps missing) connections with the study of animal behavior.

ABSTRACT. Using examples taken from bees, Tetrahymena, Boids, and some web services, I discuss  how macro and complex collective phenomena are self-organized in those natural and artificial systems, and how to analyze them. Further, I am going to discuss a new definition of super-organisms.

ABSTRACT. Bats are known as excellent hunters; they are able to deftly pursue agile prey by exploiting their high maneuverability and fine echolocation. Some bats are known to coordinate the width of sonar beam and frequency of pulse emission according to hunting phases [1,2] and to pursue prey with maintaining constant direction from prey, and decreasing range, this maneuver is considered to be effective to reach target in a short time [3]. To elucidate the tactics of the hunting in greater detail, we observed the pursuit behavior of Japanese horseshoe bats (Rhinolophus ferrumequinum nippon) targeting escaping moths under experimental conditions. We measured the direction of ultra-sonic pulses emitted by the bats with microphone-array, and those bats’ and moths’ location with cameras. As a result of these measurements, it was confirmed over several sessions that the bats became to emit pulses toward the future location of the moths as the distance between the bat and the moth decreased. This result suggested that the bats adjust pulse direction to overcome the difficulty of maintaining target in sight at a short distance. In addition, the bats switched their flight direction from toward the moths’ previous location to toward the moths’ future location, as the distance decreased. Flying toward target’s previous location is considered as an effective maneuver to maintain position behind the target. On the other hand, flying toward the moths’ future location is considered as an effective maneuver to intercept the target. Thus, it was implied that the bats chase the moths from behind of them over a long distance, and then they appropriately shift their flight mode for intercepting over a short distance. From these findings, it was suggested that bats predict the future location of prey, and then control their pulse direction to keep it in sight and adjust their flight courses according to the distance so as to capture their target efficiently.

ABSTRACT. Group-living animals always face necessity to reach a consensus and make decision. When a member of the group travels to another place for gain of resources or decrease predation risks, other individuals balance between benefit from staying there and cost for following others. In general, the first part of this travel, which called as departure, proceeds in stages, not in a moment. The proceeding of the collective departure is composed of initiation by the leader and propagation among followers. In a lot of previous studies, trends of social characteristics of initiators have been reported. However, mechanisms of propagation are still unclear. In addition, quantitative studies using tracking of individuals are needed to understand relationships between the movement of one individual and the entire group. In the present study, we focused on feral horses and demonstrate how followers’ decision-making are achieved. We followed feral horses in Serra D'Arga in Portugal. We took videoclips of groups using drone. Automatic tracking of individuals in video clips were done by UAVtracker. We used 500 images for learning and the algorithm shoed about 95% of true positive rate and precision. We categorized the types of departures. Departure was categorized to two types. We mainly analyzed time lag among followers’ responses. We found the behaviors of the leader didn’t affect recruit efficiency of followers. On the other hand, the relative distance to followers from the leader significantly affect the order of response but not time lag. Interestingly, time lag between the leader and first follower was significantly longer than those among followers. These results indicate that topological distance might affect the response to the leader but metric distance might not affect. The difference of time lag between “leader” - “first- follower” and “followers” implies that the suggestion from the leader was not enough to change the state of the entire group and first follower potentially take an important role to change the state of the entire group. Our study suggests that response to others contains a lot of randomness in feral horses. Therefore, their behavior might be governed by some behavioral rules but those might not be absolute.

ABSTRACT. When group-living animals negotiate decisions about where and when to move in the environment, they coordinate their local-scale movements to maintain cohesion amidst these larger scale decisions [1,2]. These broader space use decisions typically reflect the location and availability of resources [3-7], as well as the risk of predation associated with particular areas (i.e. “landscape of fear”) [8-10]. However, an animal group does not exist in isolation – the optimality of a group’s space use decisions is fundamentally affected by where other groups in the population decide to move and which resources they choose to exploit. Competition between groups over limited resources or mating opportunities can lead to costly aggressive encounters between groups [11-15], and the depletion or monopolization of shared resources [16-18]. Accordingly, in order to optimally use the space available to them, animal groups may incorporate the space use decisions of neighboring groups into their own decision-making processes [19-22]. Thus, social animals may exhibit not only coordination between the movements of groupmates at local scales but also population-level coordination between distinct groups at more global scales. In this study, we aimed to explore the potential for this population-level movement coordination. Using remote-sensing GPS technology, we tracked the movements and activity of four sympatric groups of olive baboons (Papio anubis), which provide an excellent system in which to study population-level coordination due their largely overlapping home ranges [23] and competitive intergroup relationships [24-26]. We carried out several analyses to assess how a baboon group’s movements affect and are affected by the presence of neighboring groups. To relax the assumption of optimality theory that animals are omniscient, we incorporated the important reality that baboons are not always aware of the location of other groups; rather, their ability to react to the location and movements of other groups is likely limited to a finite perceptual range. By recording baboon vocalizations and determining the distance of propagation, we tested how a group’s movement characteristics change when within auditory range of neighboring groups. The results of these analyses have important ecological implications, as intergroup movement coordination can affect how groups partition space and the efficiency with which they exploit the resources in the environment, thus having critical implications for the carrying capacity of the habitat [20,27,28].

[1] Couzin, I. D., Krause, J., Franks, N. R., & Levin, S. A. (2005). Effective leadership and decision-making in animal groups on the move. Nature, 433(7025), 513. [2] Sumpter, D. J. (2010). Collective animal behavior. Princeton University Press. [3] Waser, P. M., & Wiley, R. H. (1979). Mechanisms and evolution of spacing in animals. In Social behavior and communication (pp. 159-223). Springer, Boston, MA. [4] Gehrt, S. D., & Fritzell, E. K. (1998). Resource distribution, female home range dispersion and male spatial interactions: group structure in a solitary carnivore. Animal behaviour, 55(5), 1211-1227. [5] Mueller, T., & Fagan, W. F. (2008). Search and navigation in dynamic environments–from individual behaviors to population distributions. Oikos, 117(5), 654-664. [6] Nathan, R., Getz, W. M., Revilla, E., Holyoak, M., Kadmon, R., Saltz, D., & Smouse, P. E. (2008). A movement ecology paradigm for unifying organismal movement research. Proceedings of the National Academy of Sciences, 105(49), 19052-19059. [7] Morales, J. M., Moorcroft, P. R., Matthiopoulos, J., Frair, J. L., Kie, J. G., Powell, R. A., ... & Haydon, D. T. (2010). Building the bridge between animal movement and population dynamics. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 365(1550), 2289-2301. [8] Preisser, E. L., Orrock, J. L., & Schmitz, O. J. (2007). Predator hunting mode and habitat domain alter nonconsumptive effects in predator–prey interactions. Ecology, 88(11), 2744-2751. [9] Willems, E. P., & Hill, R. A. (2009). Predator‐specific landscapes of fear and resource distribution: effects on spatial range use. Ecology, 90(2), 546-555. [10] Coleman, B. T., & Hill, R. A. (2014). Living in a landscape of fear: the impact of predation, resource availability and habitat structure on primate range use. Animal Behaviour, 88, 165-173. [11] Sicotte, P. (1993). 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Behavioral Ecology and Sociobiology, 67, 875-884. DOI 10.1007/s00265-013-1510-0 [22] Seiler, N., Boesch, C., Mundry, R., Stephens, C., & Robbins, M. M. (2017). Space partitioning in wild, non-territorial mountain gorillas: the impact of food and neighbours. Royal Society open science, 4(11), 170720. [23] Bidner, L. R., Matsumoto‐Oda, A., & Isbell, L. A. (2018). The role of sleeping sites in the predator‐prey dynamics of leopards and olive baboons. American journal of primatology, 80(12), e22932. [24] Stoltz, L. P., & Saayman, G. S. (1970). Ecology and behaviour of baboons in the northern Transvaal. Annals of the transvaal museum, 26(5), 99-143. [25] Buskirk, W. H., Buskirk, R. E., & Hamilton III, W. J. (1974). Troop-mobilizing behavior of adult male chacma baboons. Folia primatologica, 22(1), 9-18. [26] Packer, C. (1979). Inter-troop transfer and inbreeding avoidance in Papio anubis. Animal behaviour, 27, 1-36. [27] Kokko, H., & Sutherland, W. J. (1998). Optimal floating and queuing strategies: consequences for density dependence and habitat loss. The American Naturalist, 152(3), 354-366. [28] López-Sepulcre, A., & Kokko, H. (2005). Territorial defense, territory size, and population regulation. The American Naturalist, 166(3), 317-329.

ABSTRACT. Luciola parvula is a kind of firefly whose adults emit flashing light. It is known among amateur observers that the flashing activity, i.e., the number of fireflies which make flashing, varies in time for about a few 10 minutes. We developed a systematic method for counting the number of flashing fireflies. In the method, processing the images of fireflies successively taken by digital camera, one can obtain time series of the number of fireflies. The method is applied to {\sl Luciola parvula} and successfully obtained temporal activities. The time variation suggests that fireflies starts/stops flashing activity by ``seeing'' activities of other fireflies and existence of communication between male fireflies is suggested.

ABSTRACT. In this contribution we present work-in-progress that develops a social coordination model of the development of stateless complex societies in southern Peru. Previous work on the Lake Titicaca Basin has appealed to evidence of warfare and evolutionary game theory, but recent insights from earlier periods in nearby regions appear to be more consistent with a model of communal ritual and collective regional development. We will present a model of the emergence of complex stateless society in the northern Lake Titicaca Basin, which is based on ritualized self-optimization of a network of social groups that shared the practice of communal rituals in sunken courts.

ABSTRACT. In this presentation, we will talk about empirical and theoretical studies on the behavioral mechanisms of frog choruses and also introduce our idea about the application of the theoretical study to the control of a wireless sensor network. We performed laboratory experiments with actual male Japanese frogs, and observed alternating chorus patterns over a short time scale as well as collective transition between a calling state and a silent state over a long time scale.Then, we proposed a mathematical model in which multiple dynamical models are switched due to a stochastic process associated with the internal dynamics of individual frogs and also the interaction with their neighbors. Numerical simulation of the model qualitatively reproduces the dynamical features of frog choruses over multiple time scales. In addition, we examine the efficacy of the proposed model as the control method of a wireless sensor network in which many sensor nodes deliver a data packet toward a gateway node due to multi-hop communication. Numerical simulation of the model with 100 sensor nodes demonstrates that the nodes can avoid packet collision with their neighbors while reducing a network power consumption.

ABSTRACT. Boid is a simple model of animal group behavior. I studied heterogenous boid models comprised of many agents which are divided into some types. With varying interaction among agents, heterogenous boid generates three stable patterns with a minimized interface between different type agents. As agents in heterogeneous boid increase, metastable patterns grow. Metastable patterns are mosaic of small clusters of the stable pattern. This means growth of the stable pattern is blocked. In this paper, to avoid metastable patterns, I propose two extended heterogenous boid models: two-component boid with noise control, and three-component boid with type-transition of agents. The extended models generate these stable patterns, suppressing metastable patterns.

ABSTRACT. Boid (Raynold 1987) is a standard algorithm for creating collaborative movements of swarming entities. Swarm members interact only locally by knowing locations and directions of their own and others. Here I propose a yet another Boid algorithm without spatial information at all. Each swarming entity knows neither of locations nor directions of itself as well as others. It can only sense signals from other members and decides its movement based on the strength of signals. Such helpless swarmers can aggregate together, follow leaders, and reunify after separation, just like the original Boid swarmers.

ABSTRACT. Bursting global activities of honey bees can be a characteristics of information cascading. By analyzing dataset of the approximately 5,000 individuals tracking data of honeybees({\it Apis mellifera}), we revealed that honeybees showed two kinds of bursting behaviors regarding their locomotion activities triggered spontaneously or externally perturbed. Honeybees' foraging and waggle dancing behavior will carry some information from the outside to the hive and non-forager bees will spread the information within a hive. By applying NMF and nMDS for classifying pioneer bees, this picture is now quantified and becomes clarified.

ABSTRACT. Honey bees are a prime example of social insect workers that change tasks as they age, in a process known as age polyethism. However, there is considerable variation among bees in the tasks they do, and when they switch between tasks. How much variation exists across different tasks, and how does early variation predict future outcomes? Are such differences due to intrinsic behavioral tendencies between bees, or are they due to the environmental factors and social interactions the bee has encountered over her life-history? To answer these questions, we introduced cohorts of newborn bees into an observation hive and used the BeesBook tracking system to monitor individual bees over their entire lifetime. Bees within a single cohort are from the same queen, born on the same day; this enables both within and among cohort analysis for nest usage, task allocation, and movement characteristics. We ask how a bees life history, nest use, and interactions with nestmates relate to the observed variability in behavior. As part of an ongoing study, these results will be used in future work to ask how differences at the level of individual bees affects the colonys overall ability to adapt and respond to environmental changes and disturbances.

ABSTRACT. The paper is an Abstarct, hence no abstract to the abstract is submitted

ABSTRACT. What is the value of communication? Why communicate at all? Let us take the example of scientific pursuit. Why do scientists bother collaborating with each other? Anyone with an Internet connection already has access to all the information needed to conduct research, so in theory, scientists could do their work alone locked up in their offices. Yet, there seems to be an important intrinsic value to exchanging ideas with peers. Repeated transfers from brain to brain seem to continually invent new concepts, theorems, and scientific theories. The mathematical structure of a society of humans, when combined with only a little experience from the world, seems to allow them to easily generalize one solution to the next. In this work, we use a population of neural networks communicating with each other, similarly to the example of cooperating scientists. By creating a network of computational learning AI agents, we create bottlenecks in information transfers, which help generalizing. This research may have important implications for the design of transfer learning techniques in AI, capable of generalizing representations through social learning to ultimately lead to a collective type of artificial general intelligence (AGI), or CAGI.

ABSTRACT. In this paper, we propose a ladder climbing robot inspired by octopus’s behavior. This robot can grasp a bar with various cross-section shapes by utilizing its soft arm, and it can climb a ladder by just repeating a simple pattern. We developed a prototype robot made of silicone, and experiments were conducted. As a result, we confirmed that the proposed soft arm is effective and the robot could climb various ladders.

ABSTRACT. Multi-legged animals show mainly two types of ipsilateral interlimb coordination. Millipedes show the direct wave gait in which the swing leg movements propagate from posterior to anterior, while some centipedes show the retro- grade wave gait in which the swing movements propagate inversely. Centipedes often oscillate their body on horizontal plane as the walking speed gets faster, while millipedes do not show this feature. However, the functional differences between those two gaits are not clear. As the purpose of this study, we hypothesize that the retrograde-wave gait rather induces body oscillation than the direct-wave gait as the functional difference, and test that hypothesis using simulation. We model the multi-legged animal by the simple springy multi-link model actuated by external forces on the links. Then we investigate the effect of direct- and retrograde wave gaits on the body oscillation. Our result shows that the retrograde-wave gait rather attenuates the body oscillation than the direct-wave gait, which contradicts our hypothesis.

ABSTRACT. Reconfigurable modular robots have a potential ability to achieve several types of task by changing its physical configuration. It is a big challenge to change their configuration appropriately based on the task in a distributed manner. To date, we have developed reconfigurable single-legged modular robots that can physically connect with each other and form a cluster with arbitrary two-dimensional configuration. In this study, we develop a distributed strategy for the robots to collectively generate appropriate configuration to traverse pre-unknown gap environment. Using dynamic simulation, we found that the proposed strategy enables the robots to traverse gap in safety with minimal number of modules.

ABSTRACT. Snake robots are capable of adapting to difficult situations, such as cluttered environments, using its many degrees of freedom. However, if one of the joints gets passive, it is generally very difficult to achieve the ordinary performance. In this paper, control of a passive joint using rolling motion is considered, with the use of crawler gait in mind. Crawler gait is a state-of-the-art motion pattern for snake robots that is capable of moving on an uneven terrain, but if there is a passive joint, the motion can be interrupted by freely moving part of the robot itself. As a key to solve this difficulty, this paper proposes to use the rolling motion, which has not been used in controlling a passive joint. A simplified model is proposed to consider the control and based on this, one simple controller is adopted. The validity of the idea of using rolling motion is tested by numerical simulations.

ABSTRACT. Small-brained insects are expert at many tasks that are currently difficult for robots especially in dealing with real-world, dynamic environments. In particular, the speed and robustness of insect learning is in stark contrast to many AI methods which take long times to train and require large amounts of labelled data. For example, the desert ant, Melophoros bagoti, is a champion navigator, able to visually navigate routes of up to 100 m through complex habitats [1] with a performance far above current map-based methods such as SLAM (simultaneous localization and mapping). Remarkably, these ants are able to learn the information needed to visually navigate 10’s of metres after only a single exposure to the route information [2]. They achieve this feat despite brains of only ~500,000 neurons and a kilo-pixel visual system (see Fig 1A for examples of low-resolution images), and this makes them ideal inspiration for engineers seeking to design resource-light control algorithms for small robots whose size makes power efficiency paramount [1]. In this spirit, we have developed a visual route navigation algorithm which replicates many aspects of ant navigation with biologically plausible computation and memory requirements (Fig 1A and [3-4]). These resource constraints mean first, that our algorithms can be used on-board fully autonomous small robots, and second, that they are amenable to swarm robotic approaches.

ABSTRACT. In this study, we develop a jumping leg mechanism for taking off a flapping flight robot. Firstly, the jumping leg mechanism which can be contracted and released by human hands was developed, and it was successful as a result of taking off experiment. However, this mechanism had to be contracted and released by human force. Therefore, secondly, we have developed a device that automatically contracts and releases the jumping leg mechanism. As a result of conducting experiments, we confirmed that a flapping flying robot can jump using this device.

ABSTRACT. Ionic Polymer-Metal Composites (IPMCs), which belong to a subset of Electroactive Polymers (EAPs), is proposed to build artificial muscle for new robotics design. However, even though there has been very promising possible usage, the study and application of IPMCs are universally neglected among classes and robotics research in colleges due to the complex and dangerous manufacturing process and high requirement in chemistry background. In order to help robotics students and researchers with little chemistry background to manufacture, utilize and explore the artificial muscle, this paper proposes a simple and safe way to lay the foundation for researchers and students to manufacture their own IPMCs artificial muscle, to study, explore and contribute to this new field of bio-inspired robotics. In doing so this paper lays a technological foundation and further develops and explores possibilities for the future development of artificial-muscle-based bio-inspired robotics.

ABSTRACT. In this research, we propose flapping robot with elastic materials for imitating muscle structure of birds. In the flapping motion of birds, two kinds of muscles play important roles, that is, pectoralis muscle and supracoracoideus muscle. Pectoralis muscle and supracoracoideus muscle work during downstroke motion and upstroke motion, respectively. Pectoralis muscle is much bigger than supracoracoideus muscle since flying force is mainly generated during downstroke motion. In this paper, we imitate the structure of bird’s muscle by using piano wires as elastic materials. When the wing moves upward, elastic energy of piano wire is stored. And the energy is released when the wing moves downward. Two type of flapping robots, which use crank mechanism and servomotors, are utilized for validating the effect of the existence of elastic materials.

ABSTRACT. It is widely believed that behaviors of cells derived from different species or different cell lines are different. This study, however, reports that a variety of forms and migration modes in isolated epithelial cells were observed even though the cells were taken from the same cell line and the experimental conditions were constant. To understand diverse formation processes in cell behavior, a simple mathematical model named as particle-fiber model was constructed where a single cell is assumed to be composed of particles and stress fibers. Here, growth process in size of particles and in thickness of fibers were introduced, which are varied depending on forces exerted on the particles. Simulation results showed a various cell shapes can be self-organized even though the parameter values, describing properties of cells and their interactions with environment, were kept constant.

ABSTRACT. Social interaction has become an increasingly popular topic in many scientific fields within recent years. In cognitive neuroscience, the study of social cognition, i.e. cognition involving others, has started to shift focus away from individual brains and towards embodied and participatory approaches, which highlights the importance of an agent’s interaction with the environment and with others. However, the role of social interaction in the understanding of social cognition remains limited, and even though interactive processes have gained importance in the study of coordination dynamics, indicating that complex patterns result from the mutual regulation of a social encounter, the mechanism(s) responsible for the coupling of two or more systems are still under debate.

Much like swarms, coupled systems can generate complex behaviors that cannot be performed in isolation. Two or more agents are said to be coupled if they are able to influence one another’s ongoing activity. The result of those influences is often synchrony, where all agents eventually function as one, unified, multi-agent system. Although different processes can underlie synchronization, oscillation synchrony (the synchronization of rhythmic or repetitive patterns of activity) has been observed among different physical, biological and social systems, ranging from clocks, fireflies, crickets, and pacemaker neurons, to people walking at the same pace and audiences suddenly clapping in unison.

The central nervous system of many animals, including human beings, produces different types of neural oscillations, which are characterized by five distinct frequency bands: delta (0.1-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), beta (12-30 Hz) and gamma (30+Hz). Oscillations are important because they provide effective means to control the timing of activity (in this case, neuronal firing), temporally coordinating information transfer and communication.

Neural communication is not always necessarily determined by anatomical connectivity. Instead, transient dynamical patterns of functional connectivity, mediated by phase synchrony, can integrate widely distributed regions of an individual brain. Phase synchrony, or coherence, occurs when the oscillatory rhythms of participating neuronal groups coincide in the phase of excitation/inhibition; this renders neural communication effective, precise and selective. Large-scale neural integration has been proposed by many authors in the field of cognitive neuroscience as responsible for the realization of different cognitive acts, and even possibly forming the basis for the unity of mind.

Neural activity of a human agent can become coupled to the physical world. When an external stimulus with a certain rhythm is presented, the ongoing oscillatory activity of the brain will reset its phase, which causes an entrainment of neural oscillations to the relevant information stream, therefore functioning as a resource for optimal processing capacities by changing response gain and amplifying neuronal responses to the events in that stream. This environment-to-brain coupling is key for the agent’s ability to retrieve information about the world in order to guide its actions.

Intriguingly, a growing number of human EEG and MEG based hyperscanning studies, which record real time electrical neural activity from the scalp of two -or more- individuals at a time, reveal that patterns of neural synchrony appear across brains during social interaction. Increased brain-to-brain synchronization of different frequencies is related to increased coordination and cooperation, better task performance, interactive decision making, joint attention, subjective reports of engagement and social connectedness, and even pain reduction and empathic accuracy. This increase is not due to similarities in stimulus input or motor output, increased stimulus complexity, or closeness of action, which suggests that neural synchrony is not a byproduct of interaction, but rather a coupling mechanism in itself.

Furthermore, brain-to-brain neural synchrony has also been reported in other animal species, such as birds. The nerve cell activity in the brain of a singing bird will change and synchronize with its partner when the partner begins to sing, making the brains of both agents essentially function as one, leading to perfect a duet.

Taken together, these findings suggest that brain-to-brain coupling during social interaction (or social coupling) works as a mechanism to guide individual actions. More importantly, they support evidence from multi-agent system computational modelling, which reveal that individual agents do not simply rely on the complex sensory stimuli from the behavior of the other agent; instead, the agents are mutually interacting and become coordinated, thereby enhancing each other’s neural and behavioral complexity in a complementary manner, creating a larger, dynamically integrated system.

Based on this, it would seem that the collective abilities that emerge from the interactions of individual organisms within a swarm could be explained by the synchronization of neural oscillatory activity, producing global functional patterns across agents and allowing the swarm to function as a unified multi-agent system, acting together to accomplish a global task. However, we ask ourselves what mechanisms other than synchrony could lead to the integration of swarming animals. Can the field of swarm modelling help us to better understand the basis of social coupling? Does work in artificial life give us clues about what other mechanisms could be operative?

ABSTRACT. Most of the studies on polyadic social interactions are limited to the individual level whilst the inter-group social relationships have been mostly studied through the dyadic relationships. A multilevel society is a society with nested levels of social organization and is characterized by the intense polyadic interactions among the groups; thus, it is both important and interesting to study group-level relationships in a social system. Their functions and mechanisms are still poorly understood, especially for non-primate species, because of the lack of quantitative data. In this study, we aimed to apply spatial association data to verify the presence of a modular structure in feral horse society using the drone technique. Drones have recently been used for behavioral study, but individual identifications from the aerial photos have been rarely attempted in the previous studies. We took aerial photos of a feral horse herd in Serra D’Arga, Portugal in 30-minute intervals using drones, identified all the individuals, and collected their position data. We could observe 126 over-one-year-old horses in total which were present at the observation site. Their interindividual distance distribution showed two clear peaks, suggesting the presence of small social organizations, i.e., “units.” We successfully defined 23 units (21 harems and 2 all-male-units; AMUs) and several solitary bachelors using the distance data. The units’ home ranges largely overlapped and their inter-unit distances were significantly smaller than the randomized data, which suggest units aggregate to form a higher-level social organization, namely a “herd.” Moreover, this herd had a structure where larger harems were more likely to be in the center, while all-male-units were in the peripheral zone. These three pieces of evidence regarding the existence of units, unit aggregation, and stable positioning among units strongly indicates that there is a multilevel structure in feral horse society. Our study has successfully provided an innovative method for the quantitative evaluation of this multilevel society. It may enable further understanding of its functions through comparison with other social indices, as well as cross-species and cross-population comparisons in future studies.

ABSTRACT. I compared ontogeny of schooling behavior between homo- and heterogeneous tadpole groups of Japanese mountain frog (Rana ornativentris). The tadpole groups measured schooling behavior every week for five weeks. The mean values of individual distance and nearest neighbor distance were decreased along with ontogeny (up to hind limbs developed). However, there was no significant difference between homo- and heterogeneous tadpole groups in these values.

ABSTRACT. Researchers in gastroenterology, microbiology and neuroscience employ animal models to investigate the role of gut microbes in socially relevant behavior. Surprisingly, despite being lab-friendly models for sociality-related questions, group-living insects receive little attention from this perspective. Nonetheless, insect social behavior research is currently undergoing a radical transition, thanks to the increasing availability of high-throughput video tracking systems. However, these video tracking systems have minimal behavioral pattern identification and perform data analysis only a posteriori on previously recorded videos. Our goal is to study how gut microbes of individual ants affect the emerging properties of the whole colony, and develop a machine-learning based behavioral pattern classifier, to help us recognizes individual behavior in real-time. This intelligent tracking system will be connected with a processing backend for simultaneous data harvesting and analysis. The device will be used to monitor laboratory ant colonies including artificially gut microbe-remodelled workers in differential proportions. Generated datasets will include individual behavior, social interactions and colony-level information. There are two main predictable scenarios: 1) microbe remodelling-mediated individual behavioral changes do not affect the emerging properties of the group; 2) colony-level properties vary based on the presence/proportion of microbe-suppressed individuals. This study would be the first attempt to investigate the role of gut microbes on whole animal societies, and the first to provide these results in real-time.

ABSTRACT. Division of labor through task allocation is a mechanism leading to higher order systems such as multicellular living systems and complex society. How they achieve the division of labor is one of the most fascinating questions in behavioral ecology, robotics and complex systems science. Social insects are the best example of adaptive complex systems which achieve various tasks through local interactions between individuals. However, it is difficult to elucidate how the systems composed of various types of many individuals achieve division of labor, and to quantify individual behavior and integrate them at a collective level. To reveal global and local level features, network analyses have been useful tools in various fields. The pattern of task allocation in social insect is a bipartite network, which has two node classes and the links are only between nodes in the different classes. Previous study showed that a bipartite approach provides useful insights into task allocation, but detailed data at the colony-level and improving method requires further investigations. Therefore, we analyzed task-individual networks. Here, we quantitatively conducted analysis on three distinct levels: individual, subnetwork (module) and the network levels. The aim of the present study is to understand how tasks are distributed among workers, to estimate the level of modularity in task-individual network as the degree of colony level specialization, to classify workers’ roles and tasks’ roles in task-individual network as regards their position within and among modules. We assessed the structure of task-individual networks with weights in 5 colonies, quantifying modularity using community detection algorithm to reveal the cluster structures. The weights on the links represent the number of executions of the tasks. To evaluate the role of individuals in the network, its among-module connectivity c, (i.e., the level to which the individuals were linked to other modules) was calculated. In all colonies, the high module structure was observed, but they don’t have complete module structures. When temporal data of day (day1, day2, and day3) was used for analysis, the same tasks were included in the same modules. These results indicated that individuals-tasks interaction patterns were basically consistent during the observation. We also found that the task-individual networks have less or anti-nested structure. We confirmed age polyethism. Interestingly, some workers often were being inactive, but worker inactivity was not correlated with age. Then, we will discuss individual-level and module-level functions through c score. Our data suggests that the bipartite approach provides useful insights into task allocation.

ABSTRACT. In general, superior intelligence is required for solving difficult problems. But many organisms, especially social insects, solve the problems using self-organization methods that do not rely on the intelligence of each individual. The Japanese subterranean termites Reticulitermes speratus is multiple-piece nester. The nest of this termite exists over several woods, and those are connected by ground-tunnels and shelter-tubes. Their nest has a complicated structure, and it looks like a maze. Termites living in such involved space are expected to have a sophisticated self-organization mechanism that can solve the maze. Here we show that termites solve the maze using a novel self-organization system that based on the excitatory transmission among individuals. We connected the maze to the termite colony and set the new resources at the goal point, and filmed their exploration behavior. The characteristics of termite exploration behavior are three points: always be with a group, quickly gathering on the correct path immediately after the first individual reached the goal, and individuals become faster after the goal. These results suggest that termites cannot solve the maze by a single individual, but the group has a mechanism to quickly solve the maze by transmitting excitement like a bucket relay.

ABSTRACT. Solitary ants use two different methods, carrying and dragging during load transportation. This study investigates how solitary ants, Formica japonica, optimize the foraging with using two different methods properly. By recording ant behavior around obstacles, we found that passing periods during dragging mode were longer than those for carrying mode. Moreover, the relation between the passing periods and the first-touch position of obstacle depended on the transportation methods.

ABSTRACT. Previous studies on the response of the pillbug (Armadillidium vulgare) to light stimuli have focused on activity such as photopositive (Increased with temperature) or photopositive at day (Low temperature reversed) for light stimuli , but positive/negative phototaxis for light stimuli have not been clearly reported. In this study, we evaluated the phototaxis of the pillbug using an omnidirectional treadmill with a cylindrical LED display. In the 1st experiment, using white light with a stimulus intensity of 830 lx, we set the stimulus direction reversal time condition (160 s, 40 s, 10 s) and measured the change in behavior of the pillbug in response to the change in the direction of the stimulus. The results showed that the phototaxis and residence time differed depending on the conditions. In the case of condition 10 s, phototaxis did not appear, but a characteristic that the residence time, which means the time without moving, was long appeared. On the other hand, negative phototaxis was confirmed under the conditions of 40 s and 160 s, resulting in a short residence time. In the 2nd experiment, the trajectories of the pillbug were measured for 15 minutes under different stimulus intensity conditions (8700 lx, 830 lx, 120 lx) using white light, and the direction of movement relative to the light stimulus direction was analyzed. The results showed that light intensity of 120 lx did not induce phototaxis, whereas light intensity of 830 lx or 8700 lx induced behavioral characteristics considered to be negative phototaxis, and the ratio of time spent traveling in the opposite direction to the stimulus was greater under the condition of 8700 lx. In conclusion, we reevaluated the phototaxis of the pillbug by measuring its trajectories under light conditions (8700 lx), which was not observed in previous studies. From the experimental results, it was shown that the negative phototaxis of the pillbug appeared strongly as the stimulus light quantity increased. It was also shown that as the frequency of change of the position of the light source in the environment increased, the time to choose not to move but to stay in the place increased. In the future, we would like to clarify in more detail what kind of mechanism is working on such action decision making.

ABSTRACT. Recent work on modeling neural networks as complex adaptive systems has revealed that the development of associate memory at the system scale could facilitate the emergence of system-wide coordination. However, so far this work has been demonstrated on small artificial neural networks with highly regular and constrained topologies. In this work, we will show the results of applying self-optimization to the C. elegans connectome modeled by either a Hopfield neural network or a continuous-time recurrent neural network.

ABSTRACT. Collective behaviour in nature provides a source of inspiration to engineer artificial collective adaptive systems, due to their mechanisms favouring adaptation to environmental changes and enabling complex emergent behaviour to arise from a relatively simple behaviour of individual entities. As part of our ongoing research, we study the social amoeba Dictyostelium discoideum in order to derive agent-based models and mechanisms that we can then exploit in artificial systems. In this paper, we focus on the stream-breaking phenomenon occurring during the aggregation phase of the life cycle of D. discoideum. Stream-breaking is augmented and sustained by the capability of cells to relay the 3’, 5’-cyclic adenosine monophosphate (cAMP) signal to their local neighbours. We provide an agent-based model with three main elements explaining stream-breaking: (1) modelling of motive force and resistance of cells; (2) quorum sensing – for identifying threshold of concentration of cAMP below which cells start losing motive force, and for identifying threshold of counting factor (CF) above which the cell-intrinsic resistance increases because of the high number of cells at the back of the stream; (3) emergence of late centres further attracting cells. Results show that the breakup of aggregation streams depends on cell density, motility, and the concentration of cAMP and CF. Breakup also comes with the appearance of late centres. Our biological experiments, using Ax2(ka) strain, show similar behaviour to our computational results. Further work will investigate the motive force during the slug formation phase of the D. discoideum life cycle, and study the relationship with age, speed and size of the slug.

ABSTRACT. Hyperheuristics form a new concept that provides a more general procedure for optimization, They give the possibility to find the best combinations of existing low-level heuristics that can solve a large number of problems without specific parameter tuning. The honey-bees mating process is a swarm-based optimization method, which is inspired from real honey-bees mating. In this paper, we propose a new hyperheuristic using Honey bee mating optimization as a strategy for choosing the best sequences of low-level heuristics in order to solve various optimization problems. The proposed hyperheuristic is implemented under the Hyflex plateform[4]. Tested on the MAX-SAT and the Bin-Packing problems, our algorithm showed good results compared to the other ten hyperheuristics participating in the CHESC challenge.

ABSTRACT. Bats use ultra-sonic wave to know their circumstance, and it is known that they can fly around in the highly crowded situation e.g., a cave. In the cave, each bat fly in the different directions, however they can manage to maintain high-speed flight without colliding others and obstacles. In this study, we observed the behavior of small number of bats in the chamber, and developed a mathematical model for their flight. Various behaviors reproduced from the numerical simulation of our model. Spontaneous traffic lane formations are also observed in the numerical simulation with a large number of units.

ABSTRACT. Animals often swarm and form communities to survive in harsh and complex environments. Towards improving the vulnerability of engineering systems against power-source limitations, we focus on food sharing community of vampire bats (Desmodus rotundus). Although vampire bats die within two days if they fail to acquire any food, they can survive over 10 years by forming a highly sophisticated community wherein they share food each other. In this study, we developed a simple mathematical model for the community formation process and demonstrated its validity via simulation.

ABSTRACT. 1. INTRODUCTION How species coexist has still been a major question in ecology. The classical theory of community ecology predicts that species sharing the same niche can’t coexist [1]. However, the phenomenon so-called "the paradox of the plankton", i.e. the coexistence of many species with a similar niche such as in food and habitat use, is observed in various biological communities [2]. We focus ant communities as a model system where multiple species with overlapping niches coexist in the field. Ant workers are generally known to be most aggressive toward unrelated individuals of the same species [3]. Such aggression is considered a counteradaptation to intraspecific workforce exploitation, such as larval abduction (slave hunting) and reproduction by the invader in the host colony [4]. Tsuji [5,6] discussed that those hostilities among conspecific ant nests can promote species coexistence as a byproduct, because the classical theory of community ecology predicts that when intraspecific competition is stronger than interspecific competition, multiple species can coexist [7]. However, empirical data about the relative strength of intra- and inter-specific competition, or more precisely data on the (conspecific and heterospecific) density dependence of population growth are scanty in ants. Here, we quantitatively estimated the effects of intra- and inter-specific competition on colony growth parameters in the ant Diacamma sp. in the field.

2. MATERIALS AND METHODS In Diacamma sp., a capture-mark-recapture of an entire intact colony is possible by using the bamboo tube trapping technique [8]. Using this technique, we started a field experiment in Sueyoshi Park, Naha from October 2018 (ongoing now.) We released captured D. sp. colonies (all individuals were marked) at various places in the park where the densities of the same species and other ant species are variable. One week later we recaptured the colonies and investigated the change in the colony contents, i.e. the number of workers and the weight and the number of broods during the 7 days. Then the effect of density of the same and other ant species on the intracolonial population growth was statistically investigated. The densities of the same and other ant species were estimated by visual observation of ant nests and by pitfall trapping of within 5 m radius from the released colonies.

3. RESULT AND DISCUSSION The survival rate of workers and the per worker brood production tended to decrease with increasing the local density of the same species. In contrast, such density dependence of other ant species on the colony performances of D. sp. colonies was not detected (at this moment of writing). Our data provide evidence for intraspecific competition that is stronger than interspecific competition in a real ant community, which has long been assumed with no direct empirical evidence .

REFERENCES [1] G. F. Gause, “The struggle for existence”, Baltimore: Williams and Wilkins, 163 p, 1934. [2] G. E .Hutchinson, “The paradox of the plankton”, The American Naturalist, Vol. 95 No. 882, pp. 137-145, 1961. [3] B. Hölldobler and E. O. Wilson, “The ants”, Harvard University Press, 1990. [4] A. Buschinger, “Social parasitism among ants: a review (Hymenoptera: Formicidae)”, Myrmecological News, Vol. 12 No. 3, pp. 219-235, 2009. [5] K. Tsuji, “What brings peace to the world of ants (Hymenoptera: Formicidae)”, Myrmecol News, Vol. 13, pp. 131–132, 2010. [6] K. Tsuji, “Kin selection, species richness and community”, Biology letters, Vol. 9 No. 6, 20130491, 2013 [7] R. A. Armstrong and R. McGehee, “Competitive exclusion”, The American Naturalist, Vol. 115 No. 2, pp. 151-170, 1980. [8] Y. Fukumoto, “A new method for studying the successive change of colony composition of the ants in the field”, Biol Mag Okinawa, Vol. 21 pp. 27–31, 1983.

ABSTRACT. In social insects, unorthodox reproductive systems such as parthenogenesis allow unusual genetic structures in their societies and provide us a unique opportunity to address basic evolutionary issues, including cooperation and conflict between relatives and the significance of sex. In the past decade, several types of parthenogenesis have been reported in various taxa of ants. The life history of these species should be clarified before testing theoretical hypothesis. Here, we provide basic ecological information of Monomorium triviale with genetic evidence for thelytokous parthenogenesis. This species is characterized by distinct queen-worker dimorphism and striking reproductive division of labor: queens produce both workers and new queens without mating, whereas workers are completely sterile. Field observation showed that their nests were usually headed by multiple queens (average of 7.26 and maximum of 34 queens per nest) and were likely to be founded by fission because the new queens are wingless. Gyne broods were produced in July to August, while no males were found. Laboratory rearing confirmed that these gynes produced workers without mating. Furthermore, we developed microsatellite markers and genotyped the mother-daughter pairs. The virgin queens and their daughter workers share the same genotypes, suggesting lowered rates of recombination. Using these ecological and genetic information, a mathematical model estimating the optimal number of queens was designed on the basis of inclusive fitness theory.

ABSTRACT. The evolution of complexity is one of the prime features of life on Earth. Although well accepted as the product of adaptation, the dynamics underlying the evolutionary build-up of complex adaptive systems remains poorly resolved. Using simulated robot swarms that exhibit ant-like group foraging with trail pheromones, we show that their self-organizing capacity paradoxically involves regulatory behavior that arises in advance. We focus on a traffic rule on their foraging trail as a regulatory trait. We allow the simulated robot swarms to evolve pheromone responsiveness and traffic rules simultaneously. In most cases, the traffic rule, initially arising as selectively neutral component behaviors, assists the group foraging system to bypass a fitness valley caused by overcrowding on the trail. Our study reveals a hitherto underappreciated role of regulatory mechanisms in the origin of complex adaptive systems, as well as highlights the importance of embodiment in the study of their evolution. This study has already been published elsewhere (Fujisawa, Ichinose & Dobata, 2019 Commun. Biol. https://doi.org/10.1038/s42003-018-0276-3).

ABSTRACT. Lévy walks, which are special cases of random walks with step lengths following a power-law distribution, are observed in a variety of biological phenomena ranging from cell and animal movements to human movements. It has been revealed that Lévy walks lead to high search efficiency because of rare long straight movements among short steps, and thus the widely observed Lévy walks are considered as a consequence of natural selection. However, there is a recent debate related to the origin of Lévy walks because some evidence of other mechanisms has been accumulated. Therefore, it is imperative to explore the diverse mechanisms depending on physical factors and ecological conditions. Although it is crucial to explore the generative model of Lévy walks, it has been less understood. Here, we develop a minimal model composed of simple deterministic nonlinear maps and show that the Lévy walk patterns of an autonomous agent can emerge near a critical point which is sitting between two regimes of internal dynamics: stable synchronization and asynchronous states. This suggests that the commonly observed Lévy walks can stem from a hypothesis that biological systems are tuned to criticality between flexibility and stability, providing new insights into understandings of how and why Lévy walks emerge widely in biological systems.

ABSTRACT. Toquenaga[1] suggested a swarm algorithm work with a single distance-decreasing signal; the Minimized Boid. In this paper, we propose tiny, extremely low-cost robots as the basis of the implementation of the Minimized Boid algorithm in the real world.

[1] Y.Toquenaga, “Minimized BOID: Aggregation, reunion, and following without spatial information”, Program of SWARM2019, 2019.

ABSTRACT. Recent prevailing declines of bumblebees all around the world need emergent measures. The number of nests rather than of foraging individuals is more informative to estimate the population size of bumblebees. But finding nests of them is quite difficult even for professional researchers. Here we propose a simple but powerful technique for estimating nest locations from foraging behaviors of bumblebees. Aided with a web application, a wide range of the public can join nest finding activities using their favorite gadgets for the Internet.

ABSTRACT. This paper investigates how well human operators can control a robot, the task of which is guiding a flock of mobile robots to their target area. An operator teleoperates a robot with limited sensing ability to lead as many robots as and to drive as fast as possible toward the goal area. The teleoperated robot has a laser range finder, a camera on the front side as a sensing device and sends the information perceived by either of them to the operator. Flocking robots make decisions using a Boid model. The flocking performance is evaluated in computer simulations.

ABSTRACT. This paper invastigates a group navigation strategy of multi-agent system using two different kinds of agents inspired by sheepdog shepherding. In a farm, a sheepdog navigates a flock of sheep, which are trained to be escaped from the sheepdog, to a given goal position. From the point of view of control system, this system fascinates robotics researchers because one or more sheepdogs, who move as a small number of controllers, can control multiple sheep indirectly. In order to demonstrate this system using group robots, we analyze the navigation performance for a minimal sheep model. We adopt a sheep model without flocking, in which sheep receives only repulsive force from the sheepdog. Next, we introduce our previous sheepdog’s controller, in which the sheepdog approaches the farthest sheep form the goal. In addition, we design a revised method of the previous controller: the sheepdog repels from the nearest sheep in order to keep suitable distance from the sheep flock. Simulation analysis shows that our proposed method can herd the flock to the goal position efficiently when navigating the flock without collecting.

ABSTRACT. This paper is concerned with the demonstration of cooperate behaviors, especially in the group alignment behavior, by the developed robots equipped with acoustic devices. Our approach is using the time-difference of sound arrival related to the distance from a microphone to the speaker, which was traditionally applied to the microphone array system to know the direction of sound source. In contrast, our proposed method, what we call, speaker array system will inform others the configuration of multiple speakers: the orientation of a robot with multiple speakers. Firstly, we conduct an experiment to examine that a robot with 3 speakers can inform the orientation to the other robot with one microphone. In addition, we attempt to apply the proposed method to align the nearby robots with appropriate combination of the microphone array system and the speaker array system. We try to realize the cooperative alignment behavior using 2 robots and 3 robots.

ABSTRACT. In the future when cars become completely driverless, traffic rules may change and cars may be allowed to move freely on two-dimensional plane by avoiding others like pedestrian flow, which could reduce traffic jams. We previously proposed a decentralized control scheme for self-driving cars that can move fast, smoothly, and safely on two-dimensional plane. However, it did not work well when cars move in the same direction. In this study, we improve our previous scheme and demonstrate via simulations that the improved scheme works better than the previous scheme.

ABSTRACT. This paper proposes a motion for passing through a spring-loaded door by using simultaneous control of two points for a snake robot. We set the head and tail of the robot as control points, and control their positions and orientations. The robot keeps the door open by controlling the head, and enters behind the door by controlling the tail simultaneously. The robot passes through the door while preventing the door from closing by pushing own body against the door. By using the proposed motion, the snake robot can enter and inspect the space which is separated by the door; snake robots can not pass through the door by traditional methods. The effectiveness of the proposed motion was demonstrated by simulations using physics simulator.

ABSTRACT. In this paper, a flexible marine riser with varying length undergoing the influence of the hydrodynamic force and an unknown disturbance to drillship is investigated. The governing equation describing the dynamics of the riser, the drillship, and the top hat is established based on the extended Hamilton’s principle. In order to suppress the lateral vibration of the riser, an adaptive boundary controller is developed. According to the Lyapunov method, the stability of the system under the boundary control and the adaptive law is proven. Finally, the efficiency of the proposed control algorithm is validated via the simulation results.

ABSTRACT. Robots offer a great possibility to be used for the monitoring of industrial and farming underwater environments, such as an aquaponics system. A current challenge is to create relatively small, autonomous, swarm capable and adaptable systems. To achieve these objectives, we present Aquabot, a robot that features a modular structure designed for future swarm applications. We present the design of the robot and detail the planned testing and necessary future advancements to verify the viability of Aquabot for deployment in a real world monitoring task.

ABSTRACT. Thermo-active hydrogels can produce energy-autonomous action by responding to thermal changes in their environment. This mimics actuation mechanisms seen in plants such as the moisture-response of pinecone scales. The lack of a simple force-characterization method means that gels are rarely used in robotic systems and hinders the adoption of new, lesser-known hydrogels for use in soft actuator designs. We propose a method for obtaining the pressure-strain characteristics of hydrogels by encapsulating them inside silicone spheres and using the measured expansion to acquire exerted pressure using the stress-strain equations for spherical pressure vessels.

ABSTRACT. In swarm robotics, collaboration of robots is one of the issue, and many cases, collaborations are based on kinetic or informatics. In this paper, we propose a state-of-the art concept of performing a new cooperative task through energy gathering using a wireless power supply system referred to as Teslasheet. To evaluate our concept, we clarify the feasibility of our new energy gathering concept for small robots using the Teslasheet wireless power supply system. Results show that the proposed concept works well.

ABSTRACT. This study tackles the task for swarm robotics where robots explore the environment to detect many targets. When a robot detects a target, the robot must be connected with a base station via intermediate relay robots for wireless communication. In our previous results, we confirmed that Levy flight outperformed the usual random walk for exploration strategy in real robot experiments. This paper investigated the performance of Levy flight varying minimum movement in navigation through a series of computer simulations and proposed the update method of the minimum movement. The results suggest that the search efficiency of Levy flight has an optimal value for minimum movement and the performance of Levy flight with the update method fell between the best and worst performance with varied parameter setting for minimum movement.

ABSTRACT. In this work, we present a novel automated procedure for constructing a metric map of an unknown domain with obstacles using uncertain position data collected by a swarm of resource-constrained robots. The robots obtain this data during random exploration of the domain by combining onboard odometry information with noisy measurements of signals received from transmitters located outside the domain. This data is processed offline to compute a density function of the free space over a discretization of the domain. We use persistent homology techniques from topological data analysis to estimate a value for thresholding the density function, thereby segmenting the obstacle-occupied region in the unknown domain. Our approach is substantiated with theoretical results to prove its completeness and to analyze its time complexity. The effectiveness of the procedure is illustrated with numerical simulations conducted on six different domains, each with two signal transmitters.

ABSTRACT. Foraging behavior to collect objects distributed in the field is one important task suitable for multirobot system. For effective performance, proper cooperation should be introduced into the robots. In this study, we propose a novel method for cooperative collective behavior of swarm robots. Once the robot finds an object, it stops there and broadcasts its position to other robots. The robots which receive the signal try to move towards the signal source and to search for another object. In our proposal, we introduce a “doubt point”, which is incremented when the robot fails to find another object. If the point exceeds given limitation, the robot ignores the signal even if it detects the signal from other robots. In this paper, we confirm the effectiveness of this algorithm in several different types of object distribution by computer simulation.

ABSTRACT. Cooperative transporting an object by Swarm robot is one of the most significant tasks on Swarm robotics. In this paper, we propose the distributed control method which realizes cooperative transportation by many robots pushing an object directly. Especially, in the proposed method, robots decide their own role autonomously, and robots transport the object effectively with keeping connectivity. Finally, simulation results are presented to verify the effectiveness of the proposed method.

ABSTRACT. Insects exhibit tremendous evolutionary success based on a bauplan of a segmented body, jointed external skeleton and small body size. The thorax of a winged insect is essentially a flying engine with powerful wing muscles that vibrate articulated external plates. Muscles of the head, legs and abdomen are also housed inside the thorax. In ants, workers are universally wingless leading to remodeling of the thorax as a power core for more effective foraging on six legs (Peeters et al. submitted). Micro-tomography allowed a detailed comparison of the geometry of muscles and skeleton in conspecific queens and workers across different lineages. Our data further indicate the importance of (1) skeleton reduction, (2) miniaturisation, in the diversification of ant workers (15000 extant species).

The thorax exoskeleton functions for mechanical protection and muscle attachment. Insect cuticle consists of chitin nanofibres embedded in a matrix of proteins, polyphenols and water. Its development has a substantial cost because ingested nitrogen is required for chitin and proteins. There is striking variation in exoskeleton thickness of workers, ranging from 1.3–1.8 μm (Anoplolepis with head width 0.56–0.61 mm) to 76.9–109.8 μm (Diacamma with head width 2.01–2.14 mm), strongly correlated with body size. Indeed, ants close to the solitary wasp ancestors show a thick cuticle, and costs of fabrication of the worker caste decreased over 100 million years of evolution. Evolutionary modifications in exoskeleton thickness represent a tradeoff between economy of material and performance of tasks outside the nests (including protection against desiccation and enemies). The consequences of thinner cuticle on muscle biomechanics need investigation.

All ant workers have a reduced middle segment of thorax resulting from the loss of wing muscles. In most formicoids (90% of extant species), this segment is considerably tapered, as opposed to poneroids where the entire thorax remains bulky. This remodelling of the flightless thorax arguably represents convergent attempts among formicoids to lower the cost of the infertile caste. Reduced per capita costs of workers allowed colony size to increase by several orders of magnitude in several lineages. In ant societies, the number of autonomous units on six legs is a critical ecological parameter – units search for food independently but can cooperate during prey capture or transport. The evolutionary shift from a few large units to many tiny units was affected by foraging needs and colonial economy. This results in increased efficiency, for example ants are key scavengers on Earth because so many units are continuously available to scout the vicinity of the nests. Empirical evidence for reduction in manufacturing costs suggests strong selection on this trait. Roughly speaking, one ponerine worker equals the weight of four formicine workers, or 14 myrmicine workers. But this ratio can exceed 300 if we select species at extremes of the ranges. This disparity is also true within species exhibiting size polymorphism in the non-reproductive caste – in Carebara diversa, one of the large soldiers weighs the same as 100 minute workers. Because ant colonies live in fixed nests, the ability to bring back maximum food is under intense selection pressure. Moreover, loss of flight means that escape is based either on running or using the venomous sting, hence strong muscles for the abdomen and legs are needed.

Despite a pronounced trend to miniaturisation of the worker caste, flightless ant workers retain their strength. Social insects show advanced cooperation among individuals made possible by chemical communication, but morphological adaptations at individual level are paramount.

Peeters C, Keller RA, Khalife A, Fischer G, Economo EPE. The evolutionary loss of flight enabled the remarkable strength of ant workers. Submitted

ABSTRACT. The strength of ants is legendary. Ants are central place foragers, meaning that workers retrieve food to the nest where the queen, brood and young workers stay. Worker ants can routinely carry items 10 times their own weight over several meters and drag objects much heavier. The origin of such strength lies in prognathy (jaws are oriented forward in ants unlike in wasps) and thorax design. Thorax is particularly well-defined in Apocrita, the dominant group of Hymenoptera. Contrary to other insects (e.g. Coleoptera), the head is distinct from the thorax and articulated with a neck. The first abdominal segment is fused to the ancestral thorax and is connected to the rest of the abdomen by a narrow constriction. Furthermore, in ants, the second abdominal segment forms the petiole and moves independently, which increases the range of motion of the abdomen. The thorax in Hymenoptera carries wings and huge wing muscles, but worker ants do not fly and lost these structures. Therefore, the thorax of ant workers is a specialized power core that moves the head, abdomen and legs [1].

Sociality and loss of flight alleviated constraints on body size in worker ants, thus permitting miniaturisation in most genera [2]. During 120 Mya of evolution, few species became large (e.g. Dinoponera, 30mm, Paraponera, 25mm, and Dinomyrmex, 28mm) while workers became minute in most extant species (e.g. Monomorium, 1.5mm, Carebara, 1.2mm, and Pheidole, 1.5mm). However, studies of individual strength were mostly done on large ants (10mm or more, e.g. Atta, Oecophylla, Messor). Attention has been drawn to collective behaviour of minute ants, neglecting their individual strength. Using laboratory observations and X-ray computed microtomography, we studied the behaviour and morphology of Carebara perpusilla, an African ant species that has the smallest known workers (1.2mm-long) and larger soldiers (3.0mm-long), allowing strong intraspecific comparisons.

We observed that workers can excavate through plaster, catch and carry springtails, and drag and carry soil pellets to bury insect corpses they feed on. Young soldiers stayed inside the nest and stored food in their distended (=replete) abdomen. Old soldiers chewed holes through the cuticle of insect corpses using their powerful mandibles and big head and guarded the nest entrance.

We found that the nervous system in the thorax consists of three ganglia that stayed relatively large in minute workers. In particular, the first ganglion occupies most of the prothorax and limits the reduction of the profurca, a cuticular infolding used for muscle attachment that rises inside the thorax. Only a tiny space exists for the oesophagus between the profurca and the dorsal exoskeleton. Furthermore, workers and soldiers had the same head and petiole muscles, but their volumes differed. Soldier to worker volume ratios were particularly high for a few muscles, reflecting an allometric scaling of these particular muscles. First, one indirect muscle that moves the head sideways was 10 times bigger in soldiers, with more fibres parallel to the axis of movement and hence more effective. Second, two petiole muscles, that move the abdomen, were 5 times larger in soldiers. We highlight morphological characteristics linked to miniaturisation and soldier specialisation, two phenomena underlying the evolutionary success of ants.

In addition, we compare the thorax morphology of Carebara to Melissotarsus, a species with 2.5mm-long workers specialized to chew tunnels through live wood [3]. Their middle legs are oriented upward so that they can chew efficiently, but workers cannot walk on flat surfaces. They have a compact thorax with fused exoskeletal plates. Petiole muscles are extremely reduced, linked to the fact that workers do not sting nor spray acid. External trochanter muscles are also reduced: these leg muscles lift up the body against gravity, but Melissotarsus workers have a unique way of walking and use their modified mid- and hindlegs to climb along narrow tunnels. We show two alternative designs of miniaturisation based on a different integration of muscles and skeleton. We suggest thorax design of minute ants vary according to their lifestyle.

REFERENCES [1] C. Peeters, R.A. Keller, A. Khalife, G. Fischer, E.P. Economo, “The evolutionary loss of flight enabled the remarkable strength of ant workers”, submitted. [2] C. Peeters, F. Ito, “Wingless and dwarf workers underlie the cological success of ants (Hymenoptera: Formicidae)”, Myrmecological News, Vol. 21, pp. 117-130, 2015. [3] A. Khalife, R.A. Keller, J. Billen, F. Hita Garcia, E.P. Economo, C. Peeters, “Skeletomuscular adaptations of head and legs of Melissotarsus ants for tunnelling through living wood”, Frontiers in Zoology, Vol. 15, No. 30, 2018.

ABSTRACT. The purpose of this research is to create new software that will automate the segmentation of micro-CT images of ants, which will give a huge time boost to the creation of segmented maps for a wide diversity of insect species. Thus, their morphological quantification and comparison will become easier and more efficient, leading to novel discoveries in evolution and genetics.

ABSTRACT. Fast movement is one of the most important traits for animals for surviving. Biologists have studied how animals evolved the design principle and the control principle for generating fast movements. On the other side, robotics engineers have investigated the design and control law of robots that behave like animals. We thus believe that understanding the biological mechanisms to generate fast movements in animals must be one of the common issues between biologists and robotics engineers. Virtually most animals have evolved variety of fast movement to escape from a potential threatening. We here focus on ultra fast movement of the ant genus Odontomachus. The ants have long and powerful mandible so called “trap jaw”. The ants use the mandible to capture preys with ultra fast movement. They also use the mandible to escape from a potential threatening. They close and hit the mandible at a ultra high speed and using the reaction force they jump away from the source of threatening. The ants move mandible using abduct and adductor muscles. Muscles are biological actuators that produce powerful and supple movements. The ants use the same muscle to generate ultra fast movements, endurance powerful movements and slow movement. On the other hand, it is still impossible for us to generate both high speed motion and strong power in the artificial systems by using the same artificial actuator. Thus, understanding ultra fast movement of the trap jaw ant must provide us a novel design and control law for artificial systems. As a first step to understand mechanisms underlying ultra fast movement of the ant, we performed X-ray micro volume imaging to analyze three dimensional structures of the musculoskeletal system and biomechanical analysis. When workers of the ant O. kuroiwae encounter a prey, they approach toward to it with opening the trap jaw and try to capture it. A prey sometimes defenses against the ant and will be a potential threatening of the ant. Then ant will have to decide the behavior to keep aggressiveness or not. We found that some of the trap jaw ants perform quick jump to escape from the source of threatening, however most of them escape from the source by darting away without jumping. This suggests to us that different internal states of them make different behavior decision against a threatening. An internal state of an animal is regulated by the neuromodulators in the brain. To unravel the role of the neuromodulators, we measured the biogenic amines in the brain by using high performance liquid chromatography (HPLC) and found brain serotonin level in those who respond with jump is significantly higher than those who respond with dart. Pharmacological experiments were then performed to confirm the role of brain serotonin. Application of serotonin precursor initiated jumping response in the ants that previously showed dart response. These experiments demonstrate the role of brain serotonin to control decision making of the jumping behavior. The jump speed of the trap jaw ants was about 0.9m/sec and power-weight ratio was 0.04kg/PS. To understand biomechanics of ultra fast movement of the mandible, we have investigated physiology of the adductor and abductor muscles. The ant was mounted on a camber to record the movement of the trap jaw using high speed digital cam and electromyography (EMG) where fine copper wires were inserted into the adductor and abductor muscles. Contraction of abductor muscles opened the mandible and the joint of the mandible was latched. Before the ant closes the mandible at an ultra high speed, adductor muscles were contracted, and the exoskeleton of the head capsule was bended. We call this phase as loading. This indicates that the ant accumulates the power of contracted adductor muscles in the bended exoskeleton to initiate ultra fast movement of the mandible. Therefore, understanding how the ant latches and releases the mandible is important issue. We then performed micro volume imagining of the musculoskeletal system of the head. X-ray micro CT imaging provides us 3D images of the exoskeletal and muscular system of the ants. The imaging elucidates the anatomical structure of the mandible muscles and structure of the joint. Contraction of the adductor muscles pulls the tendon attached on the joint to initiate loading followed by the ultrafast movement of the mandible. We identified the structure of the latching site at the joint. Live imaging using X-ray micro CT demonstrated how mandibles joint move to latch and how head capsule bends during loading. We also performed X-ray diffraction imaging of adductor muscle of the mandible using a synchrotron to analyze how muscles were contract or relax during ultra fast movement. Based on these results I will discuss neurobiology and biomechanics of ultra fast movement of the trap jaw ant.

ABSTRACT. It has been clarified that the walking frequency of a combined rimless wheel can be indirectly controlled by using an active wobbling mass via entrainment effect in the previous studies. Analyses on nonlinear properties of it have been conducted based on the theory of phase oscillation. To adapt this controlling mechanism to the more complicated systems for further generalization, different rimless wheels and an active wobbling mass are connected by a rigid rod in this study. First, we introduce the mathematical model and the indirectly controlling method. Second, we design a function that can obtain either smooth and sharp waveform to get the desired wobbling trajectory. Finally, we make a comparison between these waveforms.

ABSTRACT. In this paper, we propose a method for stable gait generation of a 3-link biped robot with damaged motor on one-side. First, we derive the dynamics and control method. Control torque between the torso and one leg is applied while another leg is controlled by reaction wheel. Second, we numerically show the period-2 gait of this dynamic walking. Finally, the gait properties are analyzed via parametric study. The results show that by adjusting the target control time for the actuated swing/stance leg separately and appropriately, potential barrier can be overcome successfully.

ABSTRACT. This paper proposes a conveyor system that achieve stable transportation on low friction surface by utilizing the high-speed crawling-like locomotion robot. First, we derive the equations of system dynamics and control. Second, object transportation using this method via numerically simulated. Third, we report the effect of viscosity coefficient on velocity of transported object.

ABSTRACT. It has been discovered by the authors that the asymmetricity of a seed-like underactuated robot assists the performance of its sliding locomotion. To easily increase the asymmetricity of these locomotion systems, this paper introduces a novel worm-like robot by simply combining two identical seed-like robots with asymmetric inner oscillation. The equations of the constraint dynamic system and control method of it are derived. Numerical simulation is conducted accordingly to verify the method. The results show that the asymmetricity of the system is highly increased and the sliding velocity becomes much faster compared with the original seed-like robot.

ABSTRACT. The penalty function method has been widely used to solve constrained optimization problems. In the method, an extended objective function, which is the sum of the objective value and the constraint violation weighted by the penalty coefficient, is optimized. However, it is difficult to control the coefficient properly because the proper control depends on each problem. Recently, the equivalent penalty coefficient (EPC) method, which is a new adaptive penalty method for population-based optimization algorithms (POAs), has been proposed. The EPC method can be applied to POAs where a new solution is compared with the old solution. The EPC value, which makes the two extended objective values of the solutions the same, is used to control the coefficient. In this study, we propose to apply the EPC method to particle swarm optimization (PSO) where a new solution is compared with the best solution found so far. In order to improve the performance of constrained optimization, a mutation operation is also proposed. The proposed method is examined using two topologies of PSO. The advantage of the proposed method is shown by solving well-known constrained optimization problems and comparing the results with those obtained by PSO with a standard constraint-handling technique.

ABSTRACT. In this study, we investigate resiliency in best-of-n decentralised decisions in which a swarm of agents (e.g. robots) need to locally coordinate in order to reach an agreement for the best quality option among n alternatives. In the literature, most methods investigated fully cooperative scenarios; here we study which decision method is more resilient to attacks from malicious agents that do not cooperate to reach an agreement for the best-quality option. Through computational models, we study to which extent different decision behaviours are resilient to different types of attacks. Once we identified the more resilient behaviours, we validate our findings with experiments on a swarm of 50 Kilobots. Obtaining similar results on different implementations supports the generality of our findings.

ABSTRACT. We elaborated our latest published work that modeled the behavioral evolution of egoistic prey individuals in a crowded environment. The simulations have demonstrated that various patterns of collective motion can emerge purely from the intraspecific competition among selfish agents, regardless of group utilities like the survival rate or foraging benefit. These findings infer natural swarm behavior could be not as intelligent if swarm intelligence refers to the improvement of overall performance through the interaction of individuals. Through introducing our findings with extended discussions, we expect to bring a new perspective on natural swarm behavior and hint some new ideas about computational swarm intelligence.

ABSTRACT. Swarm robot system is believed to be a potential solution to many tasks because of its concept of breaking complicated tasks into smaller ones. However, this property also causes difficulties to manage the system. This paper focuses on two important tasks for the system to be scalable: acquiring positions of the robots and handling communication between robots. After researching and comparing several existing swarm robot systems, a new system which uses infrared for positioning and WiFi-Mesh for communication was designed and implemented. It aims to provide a low cost, easy to build and yet a scalable system for education and research.

ABSTRACT. Brain size generally correlates with body size and brain/body size correlations have been studied in vertebrates for many decades [1]. The size of brain and brain components has attracted much attention in the context of behavioral capacities and intelligence, with an original focus on primates, including hominids [2]. Such research gave rise to the ‘social brain hypothesis’, which proposes that social group living requires increased brain capabilities reflected by brain component size [3]. Similar comparative studies have not been performed in insects, but the ‘social brain hypothesis’ has been repeatedly discussed in the context of social insects [4, 5]. More recent studies question the validity of the ‘social brain hypothesis’ in primates [6]. Other studies suggest that volumetric brain data may not well explain behavioral complexity and that instead the number of neurons more reliably predicts the behavioral and cognitive capacities of mammals or birds [7]. Unfortunately, next to nothing is known about neuron numbers in insects. Here, we compare body size, brain size and neuron number for a large sample of phylogenetically diverse hymenopteran species ranging from basal sawflies to solitary wasps and bees and to highly social bees and ants and covering an overall more than 2000-fold body mass range. We find strong correlations between body and brain mass similar to those known for vertebrates [1] and close relationship between brain mass and cell number. However, we do not find any significant differences between solitary and social insects regarding these measures. This suggests that the computational capacities of social insect brains do not substantially differ from those of solitary insects.

REFERENCES [1] Jerison H.J. (1973) Evolution of the Brain and Intelligence. Academic Press, New York [2] Holloway R.L. (1966) Cranial capacity and the evolution of the human brain. Am. Anthrop., 68: 103-121 [3] Dunbar R.I. (1998). The social brain hypothesis. Evolution. Anthropol.: Issues, News, and Reviews. 6 :178–190 [4] Godfrey R.K., Gronenberg W (2019) Brain evolution in social insects: advocating for the comparative approach. J. Comp. Physiol. A; https://doi.org/10.1007/s00359-019-01315-7 [5] O’Donnell S., Bulova S.J., Deleon S., Khodak P., Miller S., Sulger E. (2015) Distributed cognition and social brains: reductions in mushroom body investment accompanied the origins of sociality in wasps (Hymenoptera Vespidae). Proc R Soc B Biol Sci 282:20150791-. https ://doi.org/10.1098/rspb.2015.0791 [6] DeCasien A.R., Williams S.A., Higham J.P. (2017) Primate brain size is predicted by diet but not sociality. Nat. Ecol. Evol. 1:0112. https :// doi.org/10.1038/s4155 9-017-0112 [7] Herculano-Houzel S. (2011) Not all brains are made the same: new views on brain scaling in evolution. Brain Behav. Evol. 78, 22–36. doi:10.1159/000327318

ABSTRACT. How can a distributed system like a social insect colony collectively decide how to allocate resources and mature over the long-term? Many but not all species of social insects engage in the social fluid exchange of trophallaxis. In species that perform ample trophallaxis, each individual within the colony is connected through the trophallactic network, including larvae. In carpenter ants, we’ve shown that components of trophallactic fluid can influence larval development, regulating the number of new adults produced. Furthermore, we find that some trophallactic fluid proteins have been co-opted from typical insect developmental pathways: as these proteins have become abundant in this social fluid, they show increasing signatures of adaptation such as repeated duplications and positive selection. Recent advances using long-term fluorescence imaging reveal how the content and timing of larval feeding through trophallaxis controls growth and developmental timing. Thus, in species that engage in this behavior, trophallaxis and trophallactic fluid present a means by which adults can regulate larval development according to the needs of the colony.

ABSTRACT. The composition of social groups can have profound effects on their behavior and function by influencing, for example, collective decision-making or foraging efficiency. However, few social systems afford sufficient control over group composition to precisely quantify its effects on individual and collective behavior. Here, we analyze the relationship between group composition and division of labor (DOL) in a social insect with unique experimental amenability, the clonal raider ant. We use automated tracking to analyze individual and collective behavior in 120 experimental colonies with controlled variation in genetic, demographic, and morphological composition, three of the main factors expected to affect DOL in social insects. We find that heterogeneity in colony composition generates patterns of behavioral organization (e.g., behavioral ‘contagion’) that cannot be inferred from the behavior of homogeneous colonies or from the intuitive predictions of a well-studied model for DOL based on fixed behavioral response thresholds. However, these patterns can be explained by considering factors that are empirically documented but theoretically rarely considered, such as variation among ants in task performance efficiency or interactions between task demand by the brood and task performance by workers. With these additional biologically realistic sources of variation, theory can capture the full spectrum of behavioral organization observed across experimental colonies containing different types and amounts of heterogeneity.

ABSTRACT. The presentations in this symposium highlight the power and creativity of evolution by natural selection to solve challenges in functional design. In this closing talk, I will both summarize the themes of the symposium and raise questions for how biologists can best leverage our work on biodiversity to make it available and useful for technological innovation. As biologists, documenting and understanding this vast diversity of life is a core part of our mission. As we have seen in the symposium, progress toward this goal has been greatly enhanced by advances in imaging, 3D modeling, and computational analysis. There is also a long tradition of bio-inspired engineering, and we also see some of the fruits of this research approach in this conference. I raise the question how new digital imaging technologies and online platforms can be further leveraged to share biological design with non-biologists, for example through searchable online libraries of organismal forms, biomechanical structures, biomaterials, etc. The increased adoption of bio-inspired engineering would feedback on biology by increasing the relevance of our work and also helping us better understand biological mechanisms. I hope we can have a dialogue between biologists and engineers about ways to accelerate productive collaboration in the future.

ABSTRACT. This paper introduces a high speed locomotion for an underactuated locomotion robot, which consists of an arc shaped body with both a telescopic joint and a reaction wheel at the center of mass (CoM). First we show the numerical model, and then derive the equation of motion. A hierarchical control is also proposed to stabilize the dynamics. Second we show the simulation results of a speedy locomotion on a slippery level surface. Finally we discuss the stability of the reaction wheel motion.

ABSTRACT. In this paper, we propose a novel vibrating conveyor that realizes transportation of a limit cycle walker via utilizing the pull-in phenomenon. First, we confirm the entrainment phenomenon between a rimless wheel (RW) and the conveyor occurred in a specific range of a vibrating conveyor frequency via the numerical simulation using the mathematical model. Second, we show that the posture and the conveyance speed of the RW can be controlled by adjusting the vibration frequency of the conveyor.

ABSTRACT. In this paper, we propose a method to generate a stable stealth gait on frictionless road surface without double-limb support phase for a biped robot. First, we introduce a model of a biped robot with an upper body, and derive the conditions to keep the horizontal ground reaction force always zero. Next, based on the equation of motion of the linearized model, an approximate analytical solution for an appropriate initial state of the robot is derived. Furthermore, we extend the model of the robot nonlinear model. The initial state of the nonlinear model is derived based on obtained by the analysis of the linearized model, we evaluate the mathematical results obtained through numerical simulations.