Social interaction facilitates reproduction in male German cockroaches, Blattella germanica

Sociality can be beneficial for individuals because it may increase access to resources, provide greater protection from predators and create opportunities for mating. In some species, social conditions and experience also influence the physiology and behavioural responses of individuals. Although social facilitation of sexual maturation is poorly understood in insects, the German cockroach has served as an important model system for this phenomenon as group-housed females mature faster than solitary females. However, social modulation of male reproduction has not been investigated in this or any other nonpolyphenic insect species. We investigated the relative effects of social interactions and isolation on endocrine, reproductive and behavioural events during sexual maturation of B. germanica males. Results show that social interactions significantly facilitate juvenile hormone biosynthesis as well as protein production by the accessory reproductive glands, whereas isolation suppresses these processes. Other processes, such as accumulation of cuticular hydrocarbons, maturation of the male's courtship readiness and his readiness to copulate, appear to be relatively independent of social experience. However, both courtship and copulation latencies declined with age more in socially paired males than in isolated males. Our study is the first to reveal that social interactions have a profound effect on certain aspects of male reproductive physiology and behaviour in an insect species that does not exhibit phase or developmental polyphenism.