Meeting Abstract
Sexual selection can lead to dimorphic traits arising from intrasexual selection (armaments), intersexual selection (ornaments), or a combination of both. We studied the roles of body size and weaponry in the mating system of the maritime earwig Anisolabis maritima, an insect where males are more variable in size (and often larger) than females and possess asymmetrical, curved forceps instead of the straight ones seen in females. The fact that both males and female possess weaponry belies their aggressive nature and risks of injury when interacting with conspecifics, which may have implications on both courtship and fighting among potential partners. In this study, we videotaped randomly-selected pairs of earwigs and recorded their behaviors over 2 hours to determine the effects of size and weaponry on aggression vs. courtship interactions. We found that males, but not females, show size-based courtship, as smaller males were more likely to engage in courtship behavior. We also found that females, but not males, show size-based aggression, as females increase the frequency of strikes directed at males based on how large they are relative to the male. Furthermore, there is a positive relationship between the frequency of interactions and courtship behavior for females only, and this pattern is driven by the number of strikes that females direct at males. Taken together, our results demonstrate the females are more sexually receptive to smaller males with whom they engage in aggressive acts, which suggests that females may use aggression to assess the quality of or threat posed by those smaller potential partners.
