Self-organisation and communication in groups of simulated and physical robots

In social insects, both self-organisation and communication play a crucial role for the accomplishment of many tasks at a collective level. Communication is performed with different modalities, which can be roughly classified into three classes: indirect (stigmergic) communication, direct interactions and direct communication. The use of stigmergic communication is predominant in social insects (e.g. the pheromone trails in ants), where, however, direct interactions (e.g. antennation in ants) and direct communication (e.g. the waggle dance in honey bees) can also be observed. Taking inspiration from insect societies, we present an experimental study of self-organising behaviours for a group of robots, which exploit communication to coordinate their activities. In particular, the robots are placed in an arena presenting holes and open borders, which they should avoid while moving coordinately. Artificial evolution is responsible for the synthesis in a simulated environment of the robot’s neural controllers, which are subsequently tested on physical robots. We study different communication strategies among the robots: no direct communication, handcrafted signalling and a completely evolved approach. We show that the latter is the most efficient, suggesting that artificial evolution can produce behaviours that are more adaptive than those obtained with conventional design methodologies. Moreover, we show that the evolved controllers produce a self-organising system that is robust enough to be tested on physical robots, notwithstanding the huge gap between simulation and reality.Electronic Supplementary Material Supplementary material is available for this article at     

Designing pheromone communication in swarm robotics: Group foraging behavior mediated by chemical substance

In swarm robotics, communication among the robots is essential. Inspired by biological swarms using pheromones, we propose the use of chemical compounds to realize group foraging behavior in robot swarms. We designed a fully autonomous robot, and then created a swarm using ethanol as the trail pheromone allowing the robots to communicate with one another indirectly via pheromone trails. Our group recruitment and cooperative transport algorithms provide the robots with the required swarm behavior. We conducted both simulations and experiments with real robot swarms, and analyzed the data statistically to investigate any changes caused by pheromone communication in the performance of the swarm in solving foraging recruitment and cooperative transport tasks. The results show that the robots can communicate using pheromone trails, and that the improvement due to pheromone communication may be non-linear, depending on the size of the robot swarm.     

Pheromone monitoring in the field using single sensillum recording

In order to obtain direct information of stimulus dynamics perceived by a male moth under field conditions a portable device was constructed which enables continuous recording of responses from individual pheromone receptors. The device is suitable for tip recording by means of micro-knives as well as for recording with tungsten electrodes making it applicable for a wide range of insects. A micro thermistor air velocity sensor is placed within 2 mm from the preparation to record the momentary air flow. The signal conditioning electronic circuits are battery powered, and the signals can be stored on a portable tape recorder. Field recordings were made from individual male antennal pheromone receptors ofAegeria myopaeformis andAdoxophyes orana. In all recordings the instantaneous firing frequency of the receptor cells was strongly modulated by the air velocity. Analysis of the data may provide information about the average pheromone concentration and the fine structure of pheromone plumes under various conditions.     

昆虫聚集信息素

昆虫聚集信息素是昆虫重要的信息化学物质之一,对昆虫的聚集行为有重要意义。近三十年来,国外鉴定了多种昆虫聚集信息素,主要成分为一些烃、醇、醛、酮、酯、酸、酸酐、胺以及腈类化合物,但其在有害生物可持续治理中的应用潜能尚未充分利用;昆虫聚集信息素的来源多样,除蛹外,多个虫态均有聚集信息素释放,有些学者甚至把一些寄主释放的挥发物作为聚集信息素的组分;同种昆虫,不同生理状态,其聚集信息素可以完全不同或同一信息化学物质的功能不同;但是,并非所有昆虫的聚集行为均为聚集信息素调节,利他素、性信息素以及报警信息素等其它信息化学物质均能导致一些昆虫的聚集。本文综述了5目17科55种昆虫的聚集信息素。     

Insect pheromones

The evidence for intraspecies chemical communication in insects is reviewed, with emphasis on those studies where known organic compounds have been implicated. These signal-carrying chemicals are known as pheromones. There are two distinct types of pheromones, releasers and primers. Releaser pheromones initiate immediate behavioral responses in insects upon reception, while primer pheromones cause physiological changes in an animal that ultimately result in a behavior response. Chemically identified releaser pheromones are of three basic types: those which cause sexual attraction, alarm behavior, and recruitment. Sex pheromones release the entire repertoire of sexual behavior. Thus a male insect may be attracted to and attempt to copulate with an inanimate object that has sex pheromone on it. It appears that most insects are rather sensitive and selective for the sex pheromone of their species. Insects show far less sensitivity and chemospecificity for alarm pheromones. Alarm selectivity is based more on volatility than on unique structural features. Recruiting pheromones are used primarily in marking trails to food sources. Terrestrial insects lay continuous odor trails, whereas bees and other airborne insects apply the substances at discrete intervals. It appears that a complex pheromone system is used by the queen bee in the control of worker behavior. One well-established component of this system is a fatty acid, 9-ketodecenoic acid, produced by the queen and distributed among the workers. This compound prevents the development of ovaries in the workers and inhibits their queen-rearing activities. In addition, the same compound is used by virgin queen bees as a sex attractant.     

蛾类性信息素研究进展

蛾类是昆虫性信息素中研究较多的类群,已有565种的性信息素成份被鉴定,其相关研究在害虫监测和防治上得到实际应用的同时,已涉及到生态、生化、遗传等诸多方面,特别是在物种多样性的化学表达及物种的生殖隔离现象的分子水平的表达上,提供了研究的典范。本文将介绍蛾类性信息素的多样性、性信息素化学结构鉴定、微量成分的作用、合成性信息素的利用、性信息素生物合成酶、性信息素生产的调节机制及性信息素的感受机制等方面的研究现状和存在的问题。     

雄性昆虫性信息素的研究进展

全面概述雄性昆虫性信息素的研究进展。主要从性信息素的释放机制及其作用、已发现的雄性昆虫性信息素及其化学结构进行阐述。通过不同部位释放的雄性昆虫性信息素种类是多样的,但其化学结构的差异又是细微的,雄性昆虫则利用这些差异来引诱雌性昆虫、促进交配和生殖隔离等。最后对雄性昆虫性信息素的研究作了展望。     

Unexpected Effects of Low Doses of a Neonicotinoid Insecticide on Behavioral Responses to Sex Pheromone in a Pest Insect

In moths, which include many agricultural pest species, males are attracted by female-emitted sex pheromones. Although integrated pest management strategies are increasingly developed, most insect pest treatments rely on widespread use of neurotoxic chemicals, including neonicotinoid insecticides. Residual accumulation of low concentrations of these insecticides in the environment is known to be harmful to beneficial insects such as honey bees. This environmental stress probably acts as an “info-disruptor” by modifying the chemical communication system, and therefore decreases chances of reproduction in target insects that largely rely on olfactory communication. However, low doses of pollutants could on the contrary induce adaptive processes in the olfactory pathway, thus enhancing reproduction. Here we tested the effects of acute oral treatments with different low doses of the neonicotinoid clothianidin on the behavioral responses to sex pheromone in the moth Agrotis ipsilon using wind tunnel experiments. We show that low doses of clothianidin induce a biphasic effect on pheromone-guided behavior. Surprisingly, we found a hormetic-like effect, improving orientation behavior at the LD20 dose corresponding to 10 ng clothianidin. On the contrary, a negative effect, disturbing orientation behavior, was elicited by a treatment with a dose below the LD0 dose corresponding to 0.25 ng clothianidin. No clothianidin effect was observed on behavioral responses to plant odor. Our results indicate that risk assessment has to include unexpected effects of residues on the life history traits of pest insects, which could then lead to their adaptation to environmental stress.     

Pheromone-triggered orientation flight of male moths can be disrupted by trifluoromethyl ketones

In a wind tunnel trifluoromethyl ketones (TFMKs) have been found to disrupt the orientation flight of male moths to pheromone sources (virgin females or synthetic pheromone). This is demonstrated by comparison of the flight parameters of the Egyptian armyworm Spodoptera littoralis and the Mediterranean corn borer Sesamia nonagrioides, which had been topically treated with TFMKs, with those calculated for untreated insects. Inhibition occurred in all types of behavior and that of the source contact has been quantified and found to be dose-dependent. The same effect has also been noticed in Mediterranean corn borer males flying to an attraction source consisting of mixtures of (Z)-11-hexadecenyl trifluoromethyl ketone (8), a closely related analogue of the major component of the pheromone, and the natural pheromone blend. The most active TFMKs are those closest in structure to the natural pheromone, along with those chemicals which easily hydrate in solution, such as the beta-thiosubstituted derivatives. Along with the previously reported reduction of catches in the field, our results suggest the possible application of these chemicals in future new pest control strategies.     

Artificial Pheromone System Using RFID for Navigation of Autonomous Robots

Navigation system based on the animal behavior has received a growing attention in the past few years. The navigation systems using artificial pheromone are still few so far. For this reason, this paper presents our research that aim to implement autonomous navigation with artificial pheromone system. By introducing artificial pheromone system composed of data carriers and autonomous robots, the robotic system creates a potential field to navigate their group. We have developed a pheromone density model to realize the function of pheromones with the help of data carriers. We intend to show the effectiveness of the proposed system by performing simulations and realization using modified mobile robot. The pheromone potential field system can be used for navigation of autonomous robots.     

Task partitioning in swarms of robots: an adaptive method for strategy selection

Task partitioning is the decomposition of a task into two or more sub-tasks that can be tackled separately. Task partitioning can be observed in many species of social insects, as it is often an advantageous way of organizing the work of a group of individuals. Potential advantages of task partitioning are, among others: reduction of interference between workers, exploitation of individuals?? skills and specializations, energy efficiency, and higher parallelism. Even though swarms of robots can benefit from task partitioning in the same way as social insects do, only few works in swarm robotics are dedicated to this subject. In this paper, we study the case in which a swarm of robots has to tackle a task that can be partitioned into a sequence of two sub-tasks. We propose a method that allows the individual robots in the swarm to decide whether to partition the given task or not. The method is self-organized, relies on the experience of each individual, and does not require explicit communication between robots. We evaluate the method in simulation experiments, using foraging as testbed. We study cases in which task partitioning is preferable and cases in which it is not. We show that the proposed method leads to good performance of the swarm in both cases, by employing task partitioning only when it is advantageous. We also show that the swarm is able to react to changes in the environmental conditions by adapting the behavior on-line. Scalability experiments show that the proposed method performs well across all the tested group sizes.     

Chemical Profiles of Two Pheromone Glands Are Differentially Regulated by Distinct Mating Factors in Honey Bee Queens (Apis mellifera L.)

Pheromones mediate social interactions among individuals in a wide variety of species, from yeast to mammals. In social insects such as honey bees, pheromone communication systems can be extraordinarily complex and serve to coordinate behaviors among many individuals. One of the primary mediators of social behavior and organization in honey bee colonies is queen pheromone, which is produced by multiple glands. The types and quantities of chemicals produced differ significantly between virgin and mated queens, and recent studies have suggested that, in newly mated queens, insemination volume or quantity can affect pheromone production. Here, we examine the long-term impact of different factors involved during queen insemination on the chemical composition of the mandibular and Dufour''s glands, two of the major sources of queen pheromone. Our results demonstrate that carbon dioxide (an anesthetic used in instrumental insemination), physical manipulation of genital tract (presumably mimicking the act of copulation), insemination substance (saline vs. semen), and insemination volume (1 vs. 8 µl) all have long-term effects on mandibular gland chemical profiles. In contrast, Dufour''s gland chemical profiles were changed only upon insemination and were not influenced by exposure to carbon dioxide, manipulation, insemination substance or volume. These results suggest that the chemical contents of these two glands are regulated by different neuro-physiological mechanisms. Furthermore, workers responded differently to the different mandibular gland extracts in a choice assay. Although these studies must be validated in naturally mated queens of varying mating quality, our results suggest that while the chemical composition of Dufour''s gland is associated with mating status, that of the mandibular glands is associated with both mating status and insemination success. Thus, the queen appears to be signaling both status and reproductive quality to the workers, which may impact worker behavior and physiology as well as social organization and productivity of the colony.     

信息化合物对昆虫行为的影响

本文综述了来自寄主植物的挥发性物质和同种昆虫或异种昆虫释放的各种信息素及两者的协同作用的信息化合物对昆虫行为的影响。特别强调了寄主植物的气味物质和昆虫信息素协同作用在昆虫寻找寄主、求偶、交配及天敌在寄主识别过程中的重要地位。昆虫对寄主植物的识别是由于识别了植物气味的由一定组分、按照严格比例组成的化学指纹图。昆虫信息素与植物挥发性物质相结合为昆虫寻找求偶、交配场所提供更复杂或更全面的信息。许多昆虫只有在寄主植物或寄主植物气味存在时 ,才能释放性或聚集信息素。天敌在寄主识别、搜索及定位等一系列过程中 ,来自寄主的食料、寄主本身及两者的互作的信息化合物起重要的作用。研究信息化合物对昆虫行为的影响可以探索昆虫各种行为的内在机理 ,更好的了解寄主—昆虫—天敌三层营养关系的相互作用 ,对利用天然活性化合物防治害虫及生物防治提供理论依据     

Olfactometric evidence for aggregation pheromone production by females of the four-eyed fir bark beetle <Emphasis Type="Italic">Polygraphus proximus</Emphasis> Blandf. (Coleoptera,Curculionidae: Scolytinae)

Chemical communication of the four-eyed fir bark beetle Polygraphus proximus Blandf., an aggressive invasive pest of the Siberian fir Abies sibirica Ledeb., was experimentally studied using a four-way olfactometer of a modified design, in which the tested insects were allowed to move on their own from a lightproof plastic container onto the lighted arena. Young hibernated adults of P. proximus were offered four variants of odor: fir log segments infested with (1) 10 males, (2) 10 females, (3) 10 couples of P. proximus, and (4) clean air as the control. The pheromone of P. proximus was shown to be produced by females; a similar response of both sexes characterized it as an aggregation pheromone. All the three variants with infested fir logs were much more attractive than the control variant with clean air. Volatiles from fir tissues not only seem to serve as markers facilitating host selection by the first-to-arrive beetles before direct contact with the tree bark, but also to be used as pheromone precursors or synergists. The absence of difference in response to the logs infested with males and couples of the bark beetle indicated that pheromone synthesis was inhibited after couple formation.     

Spatial representation of alarm pheromone information in a secondary olfactory centre in the ant brain

Pheromones play major roles in intraspecific communication in many animals. Elaborated communication systems in eusocial insects provide excellent materials to study neural mechanisms for social pheromone processing. We previously reported that alarm pheromone information is processed in a specific cluster of glomeruli in the antennal lobe of the ant Camponotus obscuripes. However, representation of alarm pheromone information in a secondary olfactory centre is unknown in any animal. Olfactory information in the antennal lobe is transmitted to secondary olfactory centres, including the lateral horn, by projection neurons (PNs). In this study, we compared distributions of terminal boutons of alarm pheromone-sensitive and -insensitive PNs in the lateral horn of ants. Distributions of their dendrites largely overlapped, but there was a region where boutons of pheromone-sensitive PNs, but not those of pheromone-insensitive PNs, were significantly denser than in the rest of the lateral horn. Moreover, most of a major type of pheromone-sensitive efferent neurons from the lateral horn extended dendritic branches in this region, suggesting specialization of this region for alarm pheromone processing. This study is the first study to demonstrate the presence of specialized areas for the processing of a non-sexual, social pheromone in the secondary olfactory centre in any animal.     

Queen pheromone modulates the expression of epigenetic modifier genes in the brain of honeybee workers

Pheromones are used by many insects to mediate social interactions. In the highly eusocial honeybee (Apis mellifera), queen mandibular pheromone (QMP) is involved in the regulation of the reproductive and other behaviour of workers. The molecular mechanisms by which QMP acts are largely unknown. Here, we investigate how genes responsible for epigenetic modifications to DNA, RNA and histones respond to the presence of QMP in the environment. We show that several of these genes are upregulated in the honeybee brain when workers are exposed to artificial QMP. We propose that pheromonal communication systems, such as those used by social insects, evolved to respond to environmental signals by making use of existing epigenomic machineries.     

Exploitation of insect vibrational signals reveals a new method of pest management

Food production is considered to be the main source of human impact on the environment and the concerns about detrimental effects of pesticides on biodiversity and human health are likely to lead to an increasingly restricted use of chemicals in agriculture. Since the first successful field trial, pheromone based mating disruption enabled sustainable insect control, which resulted in reduced levels of pesticide use. Organic farming is one of the fastest growing segments of agriculture and with the continuously growing public concern about use of pesticides, the main remaining challenge in increasing the safety of the global food production is to identify appropriate alternative mating disruption approaches for the numerous insect pests that do not rely on chemical communication. In the present study, we show for the first time that effective mating disruption based on substrate-borne vibrational signals can be achieved in the field. When disruptive vibrational signals were applied to grapevine plants through a supporting wire, mating frequency of the leafhopper pest Scaphoideus titanus dropped to 9 % in semi-field conditions and to 4 % in a mature vineyard. The underlying mechanism of this environmentally friendly pest-control tactic is a masking of the vibrational signals used in mate recognition and location. Because vibrational communication is widespread in insects, mating disruption using substrate vibrations can transform many open field and greenhouse based farming systems.     

Food and humidity affect sex pheromone ratios in the stink bug, Euschistus heros

Abstract.  Male stink bugs, Euschistus heros , only produce the three-component sex pheromone blend consisting of methyl-(2 E ,4 Z )-decadienoate, methyl-2,4,6-trimethyldodecanoate and methyl-2,4,6-trimethyltridecanoate in a constant ratio of 53 : 3 : 44, respectively, when provided with a food source (green beans, Phaseolus vulgaris ). When volatiles are collected from insects with drinking water, humidified air, or under dry conditions, the insects stop producing two components (methyl-2,4,6-trimethyldodecanoate and methyl-2,4,6-trimethyltridecanoate) after 1 day and increase the amount of defensive compounds produced [e.g. ( E )-2-hexenal, decane]. Methyl-2,4,6-trimethyltridecanoate is able to change the behaviour of females but not males. Dual-choice olfactometer bioassays with synthetic standards of all three components, as well as the ternary mixture in the correct ratio, induce a response from females but not males, indicating that all three components have a role in sexual communication. Thus, the dietary conditions under which volatile collections are carried out are crucial for determination of the precise sex pheromone blend.     

Semiochemicals and bark beetle populations: Exploitation of natural phenomena by pest management strategists

An analysis of semiochemical communication between host trees, bark beetles and commensal or entomophagous insects discloses five principal means by which semiochemicals can influence the population dynamics of bark beetles. These are: mediation of aggregation and mass attack on new hosts, cessation of aggregation and shifting of attack to uninhabited hosts, induction of aggregation by competing species, inhibition of aggregation by competing species, and mediation of host finding by commensal and entomophagous insects. Further analysis suggests major points of natural vulnerability which lead to six fundamental strategies for potential pest management: prevention of production of aggregation pheromones, sabotage of olfactory perception, exploitation of semiochemical-based secondary attraction, exploitation of antiaggregation pheromones, exploitation of repellent allomones, and exploitation of the kairomonal response by entomophagous insects. Investigations of the many possible tactics arising from these strategies have led to three types of operational pest management programs: prevention of pheromone production by excluding bark beetles from their hosts; suppression of bark beetle populations through the utilization of semiochemical-baited traps, trees or logs; and the use of antiaggregation pheromones to protect vulnerable hosts from attack.