Male Head Secretion Triggers Copulation in the Dwarf SpiderDiplocephalus permixtus

Abstract

AbstractThe term nuptial feeding is applied for any possible form of transfer of substances during the course of mating. However, the underlying functions can range from increased coupling efficiency or increased male survival to various levels of sexual selection. Males of many dwarf spider species (Erigoninae: Linyphiidae; Araneae) produce secretions from conspicuous grooves or elevations on their prosoma that seem to play a role during the mating episode. We asked if these structures represent a survival strategy, a mating effort in that they function as a mate attractant or as a mechanism to secure matings or if they simply facilitate successful genital coupling. InDiplocephalus permixtusmales possess a deep groove in the ocular area into which females sink their chelicerae before mating commences. Secretory glands in the area of the groove produce a substance, which is taken up by the female in the process of mating. We experimentally prevented females from taking up secretion by covering the head structures of one group of males and compared the behaviour with controls. We investigated effects in a single male setting as well as in a competitive two‐males setting. Under both experimental conditions the probability that copulation occurred was significantly reduced in head covered males: females bit into male head structures irrespective of male treatment but covered males did not commence pedipalp insertion despite optimal mating position. Our data suggest that in contrast to other gustatorial arthropod species investigated so far the head–mouth contact between the sexes primarily triggers the mating behaviour of the male and not that of the female. Clearly, the secretion does not function as a mate attractant as mating position was achieved with similar probability in covered and control males. A function as a survival strategy can be excluded as well, because sexual cannibalism never occurred. Potential stimulating or manipulative effects of the secretion during copulatory and post‐copulatory phases remain to be investigated.