Influence of kin selection on cannibalism in successive instars of phidippus audax (araneae: salticidae)

Kin selection is common in nature among cannibalistic organisms that have a high kin encounter rate. The jumping spider Phidippus audax (Araneae: Salticidae) has a high, localized population density and is widely distributed. We studied the effects of kinship on cannibalism in the second through the seventh instars of this species. We observed low levels of cannibalism in second instars and high levels in fourth through seventh instars, with no effects of relatedness in those stages. In the third instar, siblings avoided cannibalism, and non-siblings were highly cannibalistic. Starvation results were similar with the only significant difference occurring in the third instar where starvation was significantly higher in related versus unrelated pairs. These results may indicate an age-dependent instinctive response among spiderlings that determines whether or not they will starve rather than confront and attempt to cannibalize their own kin.