Collective behavior based on self-organization has been shown in group-living animals from insects to vertebrates. These findings have stimulated engineers to investigate approaches for the coordination of autonomous multirobot systems based on self-organization. In this experimental study, we show collective decision-making by mixed groups of cockroaches and socially integrated autonomous robots, leading to shared shelter selection. Individuals, natural or artificial, are perceived as equivalent, and the collective decision emerges from nonlinear feedbacks based on local interactions. Even when in the minority, robots can modulate the collective decision-making process and produce a global pattern not observed in their absence. These results demonstrate the possibility of using intelligent autonomous devices to study and control self-organized behavioral patterns in group-living animals.

Group-living animals are often faced with choosing between one or more alternative resource sites. A central question in such collective decision making includes determining which individuals induce the decision and when. This experimental and theoretical study of shelter selection by cockroach groups demonstrates that choices can emerge through nonlinear interaction dynamics between equal individuals without perfect knowledge or leadership. We identify a simple mechanism whereby a decision is taken on the move with limited information and signaling and without comparison of available opportunities. This mechanism leads to optimal mean benefit for group individuals. Our model points to a generic self-organized collective decision-making process independent of animal species.collective behavior ͉ nonlinear dynamics ͉ self-organization

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The cuticular hydrocarbons (CHCs) of the ant Lasius niger are described. We observe a high local colony specificity of the body cuticular profile as predicted for a monogynous and multicolonial species. The CHCs show a low geographical variation among different locations in France. The CHCs on the legs also are colony specific, but their relative quantities are slightly different from those on the main body. For the first time, we demonstrate that the inner walls of the ant nest are coated with the same hydrocarbons as those found on the cuticle but in different proportions. The high amount of inner-nest marking and its lack of colony-specificity may explain why alien ants are not rejected once they succeed in entering the nest. The cuticular hydrocarbons also are deposited in front of the nest entrance and on the foraging arena, with a progressive increase in n-alkanes relative amounts. Chemical marks laid over the substrate are colony specific only when we consider methyl-branched alkanes. Our data confirm that these "footprint hydrocarbons" are probably deposited passively by the contact of ant tarsae with the substrate. These results suggest that the CHCs chemical profiles used by ants in colony recognition are much more complex than a single template: ants have to learn and memorize odors that vary depending on their context of perception.

Honeydew is the keystone on which ant–aphid mutualism is built. The present study investigates how each sugar identified in Aphis fabae Scopoli honeydew acts upon the feeding and the laying of a recruitment trail by scouts of the aphid‐tending ant Lasius niger Linnaeus, and thus may enhance collective exploitation by the ant mutualists. The feeding preferences shown by L. niger for honeydew sugars are: melezitose = sucrose = raffinose > glucose = fructose > maltose = trehalose = melibiose = xylose. Although feeding is a prerequisite to the launching of trail recruitment, the reverse is not necessarily true: not all ingested sugar solutions elicit a trail‐laying behaviour among fed scouts. Trail mark laying is only triggered by raffinose, sucrose or melezitose, with the latter sugar being specific to honeydew. By comparing gustatory and recruitment responses of ant foragers to sugar food sources, the present study clarifies the role of honeydew composition both as a source of energy and as a mediator in ant–aphid interactions. Lasius niger feeding preferences can be related to the physiological suitability of each sugar (i.e. their detection by gustatory receptors as well as their ability to be digested and converted into energy). Regarding recruitment, the aphid‐synthesized oligosaccharide (melezitose) could be used by ant scouts as a cue indicative of a long‐lasting productive resource that is worthy of collective exploitation and defence against competitors or aphid predators.

insects, an interesting question about animals that cooperate during foraging is the relation between the physiological status (e.g. food deprivation level), modulation of inter-individual communication and the resulting collective behaviour. Currently, this relation between starvation level and the probability that an individual will initiate, maintain or stop collective foraging is still poorly studied.Many studies have shown that social insects select efficient foraging strategies according to food quality, food quantity, distance to food source, risk of predation, or competition. Among all these variables, starvation level is one of most important parameters affecting collective foraging behaviour in ants (Cassill and Tschinkel, 1995;Cosens and Toussaint, 1986;Hölldobler, 1971;Roces and Hölldobler, 1996;Traniello, 1977), honeybees (Seeley, 1995;Schulz et al., 1998;Schulz et al., 2002; and bumble bees (Cartar and Dill, 1990). Aphidtending ant species, such as Lasius niger, are good biological models to study the behavioural flexibility of animals faced with fluctuations of nutritional supplies. Honeydew is the main source of protein and carbohydrates for aphid-tending ants (Auclair, 1963;Hölldobler and Wilson, 1990) and its production undergoes important temporal variations in the course of year (El-Ziady and Kennedy, 1956;Sakata, 1994;