Ants can be beneficial agricultural agents as they are generalist predators. However, their tending of pest hemipterans is problematic. We examined if we can disrupt such mutualism. First, we analyzed nutrient contents of honeydew and their attraction to ants. Trisaccharides such as melezitose provided high nutrient values to ant as already known, but ant preference was not in parallel with their nutrient values when comparted among various sugars. In a series of experiments, we revealed that ants use methylalkanes of the mutualistic aphid's CHCs to recognize partners, and that ants learn them well. Furthermore, those information on the mutualists were shared by colony members through trophallaxis. Finally, we found that the frequency of ant tending on pink pineapple mealybug decreased when ants were provided with artificial honeydew (sucrose solution) as an alternative food source. However, mortality of mealybugs due to parasitism did not statistically significantly differ.

For better understanding of how evolution of traits related to interspecific interactions, such as sexual selection, mate competition, social or cooperative behavior, sexual reproduction, affected community dynamics and structure, we took three approaches based on review, theoretical and empirical research. Our theory suggests that adaptation driven by interspecific mate competition or sexual conflict may enhance multi-species coexistence by strengthening self-regulation intensities of populations or weakening interspecific competition. Indeed, some earlier reports can be viewed as special cases of our more general theory. Empirical studies using bean beetles or fish also gave evidence that traits linked to intraspecific relationship affect interspecific interactions and community dynamics,

We studied the mechanism of biological invasion by comparing ecology and genetics between native Japanese populations and introduced North American populations of Brachyponera chinensis ant. DNA information suggested a genetic bottleneck at invasion, but contrary to common belief, sociobiological and demographic traits of colonies such as intracolony relatedness remained unchanged. Regardless of native or introduced all populations the ant showed a unique life cycle; establishment by outbreeding queens and inheritance by offspring inbred females and males. Radiocarbon isotope analysis suggested that the ant has changed from being a specialist termite hunter in its natural distribution to a generalist predator in North America. These results suggest that pre-adaptation, such as inbreeding tolerance, and ecological release owing to the absence of a co-evolutionary history with the background community may be important factors in the success of the invasion.

We addressed questions on interaction between different levels of the biological hierarchy in order to integrate micro and macro ecologies. We especially focused on the relationship between intra-specific dynamics, such as kin selection and sexual selection, and inter-specific dynamics, such as host-parasite dynamics and model-mimic dynamics, in the community through theoretical and empirical approaches. We empirically showed examples (though some are yet potential) of such adaptive dynamics in ants, clonal plants, butterflies, fish and other systems.

We obtain results of this study as follows: 1. We proposed a mathematical model of swarm behavior based on observation of animals. 2. We constructed control strategies of swarm based on mathematical analysis using multi-agent simulation. 3. We developed legged-modular robots as an example of swarm robots and carried out experiments to demonstrate validity of analysis and control strategies. We made a bridge between biologists and engineers.

In order to explore the phylogeographic origin and expansion patterns of invasive sweetpotato weevil Cylas formicarius and the bigheaded ant Pheidole megacephala, we conducted field survey mainly in the African Continent and Madagascar, and then performed phylogeographic and network analyses based on molecular genetic data. In C. formicarius, samples from Madagascar constituted monophyletic clade together with those from India, suggesting that the weevils originated in Gondwanaland and then had spread their distribution via conjoined Madagascar and India which had been split off from Gondwanaland. The phylogenetic studies on P. megacephala are ongoing in consideration of the species status and classification.

PPopulation dynamics is fundamental when studying pest control and conservation of biodiversity. In ants empirical data on population dynamics are scanty due to difficulty coming from their eusociality and underground life. To breakthrough this we focus on Oecophylla. smaragdina population in oil palm plantations in Malaysia. By an extensive sampling of nests, we conclude that just multiplying the average worker number per nest, 6300+2460SE, and the total nest count is appropriate to estimate population density of workers. This is the first step for long-term monitoring of population dynamics of this ant in the field. Microsatellite DNA data suggest that the average intra-nest genetic relatedness was 0.49, with some portion of colonies being polygynous and/or polyandrous. The number of ant species nested in an oil palm tree was also monitored by cutting a few trees. Admittedly, future studies should develop a non-invasive methodology to relate the weaver ant density and biodiversity.

We aim at comprehensively testing all existing hypotheses of biological invasion in ants by focusing on Brachyponera (Pachycondyla)chinensis that has been invaded from East Asia to North America. Our polulation genetic, chemical and behavioral study revealed that their population and social structure was polygyny-polydomy and multicolonial that was qualitatively the same between the introduced (USA) and the native (Japan) ranges. However, in the USA their density was higher than in Japan. The stable isotope analysis suggested a shift in the trophic level or food niche, i.e. this ant is a specialist hunter of termites in Japan but has become a generalist predator in the USA. The pupal mortality presumably correlated to the infection lord was higher in Japan. Those results suggest that as the mechanism of biological invasion of this ant the ecological release is more important than social insect-specific mechanisms such as genetic bottleneck.