Influential Interactions: Group Dynamics of the Maritime Earwig, Anisolabis maritima

Abstract

Dispersion patterns of individuals within a group can reveal important aspects about social interactions and the mating system of the species. Our study examined the distribution patterns of the maritime earwig, Anisolabis maritima, to determine the influence of sexual selection on the mating system. Male and female Anisolabis maritima both possess weaponry – however, females are very aggressive whereas males are tolerant of cohabitation, which led us to hypothesize that leks might be forming, or that aggressive females would maintain territories that would control the group environment. We examined single-sex and mixed-sex groups of 18 earwigs in a large enclosure throughout their active period to determine whether they were distributing themselves randomly, uniformly, or in clumps. We found that, in single-sex groups, males form clumps and females form uniform territories. Mixed-sex groups are uniform at first and become clumped, where females controlled uniformity and males changed their behavior in response to females. We also conducted a series of trials between three individuals, either single-sex groups or mixed-sex groups with two different-sized individuals of one sex and one individual of the other, to examine sexual selection and cohabitation preferences. Among single-sex groups, we found that females were unwilling to cohabitate, and small females were more likely to be excluded from shelters than large females – in single-sex male groups, however, males were willing to cohabitate, with small and medium-sized males equally likely to be excluded. Among mixed-sex groups we found a preference for smaller opposite sex partners, but the patterns suggest assortative mating.