The male genitalia of many invertebrate species are often elaborate, more elaborate than what is necessary for the relatively simple act of sperm transfer. These flamboyant morphologies may be the result of sexual selective processes similar to those which produce elaborate secondary sex characteristics such as brilliant plumage, antlers, or large body size The study investigated palp morphology and male reproductive success in Nephila clavipes, a neo-tropical orb-weaving spider. First, males were placed with sexually receptive females and reproductive activity was recorded and correlated with aspects of gross and palpal male morphology. Second, sperm uptake and storage were assessed by sacrificing mated females and counting the number of sperm within their spermathecae by means of a computer imaging system. The number of sperm counted was then correlated with aspects of male copulatory behavior and morphology. Third, sperm utilization was evaluated by permitting mated females to oviposit and then counting the percentage of eggs in clutch that eventually hatched. Finally, the effect of conductor breakage was evaluated by assessing the timing of its occurrence and its influence on sperm transfer There was less variation in palp size of male Nephila than in other aspects of male morphology. The distribution of palp size was essentially normal, indicating stabilizing selection. Palp size and gross male size were positively correlated. Gross male body size was the best predictor of how much sperm was produced, transferred to, and stored by the female. Size of the male was not related, however, to the percentage of sperm actually transferred. Having smaller palps did not result in any obvious compensatory behavioral strategies. Time of mating influenced how many sperm were retained by the female but there appeared to be little relationship between copulatory behavior itself and the amount of sperm later found. None of the variables analyzed in this study greatly influenced the percentage of eggs eventually hatching. Conductor breakage seriously interfered with sperm transfer but occurred less often than expected and did not appear to be a result of copulatory activity. These findings suggest that, within the parameters of this study, intersexual selection through female choice is not a significant process in this species
