Social Influences

Social behavior in cockroaches, as in other insects (Tal-lamy and Wood, 1986), is largely a function of the type, accessibility, abundance, persistence, predictability, and distribution of the food resources on which they depend. Large cockroach aggregations are found only where food is consistently renewed by vertebrates (bats, birds, humans). Biparental care is found only in wood-feeding cockroaches, whose diet is physically tough, low in nitrogen, and digested in cooperation with microorganisms. Young developmental stages in both aggregations and families rely at least in part on food originating from fellow cockroaches. Although predation pressure can alter social structure (Lott, 1991), and has been suggested as a selective pressure in cockroaches (Gautier et al., 1988), data with which we can evaluate its influence are scarce. Reproductive mode is unrelated to gregariousness; both oviparous and ovoviparous cockroaches aggregate. Subsocial cockroaches, however, are almost exclusively ovo-viviparous. While the costs and benefits of social behavior for other developmental stages vary with a wide variety of factors, the benefactors in most cockroach social systems are young nymphs. Several uniquely blattar-ian characteristics influence cockroach social structure, such as the ability to mobilize stored nitrogenous reserves and the need for hatchlings to acquire an inoculum of gut microbes. Cockroaches also display similarities to not only other insect but also to vertebrate social systems (e.g., altricial development). They are thus potentially excellent models with which to test general hypotheses in social ecology.

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