Dissertation Research: Behavioral Selection in Insects

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ABSTRACT Sherman & Andrade IBN 96-23182 An Investigation of Selection for Male Sacrifice Behavior Males of many arthropod species contribute nutrients to their mates during courtship or copulation ( nuptial feeding ). Such cases, particularly among the insects and spiders, are interesting because they represent deviations from the more typical mating pattern of male polygyny with little material investment. The functional significance and ecological conditions controlling increased male investment in insects has been a topic of interest for behavioral ecologists and evolutionary biologists. The proposed project will increase understanding of mating systems where males provide nuptial gifts by determining the conditions under which the most extreme type of male nuptial feeding -- male copulatory suicide--can be selected. This project is a comparative study of two congeneric spider species (Latrodectus hasselti and L. geometricus) in which males appear to sacrifice themselves to females during copulation. Field observations of daily movements, courtship behavior and mating success will be combined with staged laboratory interactions and estimations of reproductive output to characterize the mating system, selective pressures, and demographic characteristics of these two species. Information gathered from this species will be used to produce a model for the selection of male copulatory suicide that will place the behavior within the existing framework of sexual selection theory.