Female preference for multiple partners: sperm competition in the hide beetle, Dermestes maculatus (DeGeer).

Explanations for the evolution of polyandry emphasize either direct benefits or indirect genetic benefits. The former class of explanation predicts that females may seek multiple copulations but not necessarily multiple partners, while the latter predicts that females will seek multiple copulations with different partners. We investigated these predictions experimentally in the hide beetle, in which females mate more than once during their reproductive cycle. Female hide beetles remated more readily with novel males than with their previous partners, suggesting they mate multiply in order to obtain indirect, genetic benefits. In double-mating experiments with sterile males, the proportion of eggs fertilized by the second male was highly variable; this could not be explained by variation in male body size, duration of copulation or mating order. Male hide beetles form postinsemination associations by riding on the backs of females. This behaviour was more prevalent in the presence of rival males and less prevalent in the presence of additional females, suggesting that the behaviour serves to increase paternity, perhaps by obtaining additional copulations. Copyright 1999 The Association for the Study of Animal Behaviour.