Eat, Prey, Love: Sex influences nest intruder behavior in the maritime earwig (Anisolabis maritima)

Abstract

The most common form of parental care in insects is the guarding of eggs/juveniles from intruders. The maritime earwig (Anisolabis maritima), an insect found on beaches worldwide, is an excellent organism for studying parental care because they are found in high densities under driftwood during the breeding season. As a result, egg-guarding mothers encounter many types of intruders and are especially threatened by conspecifics that often cannibalize eggs. We studied how sex affects nest intruder behavior by monitoring the behavior of size-matched intruders of different sexes in an arena with a mother and her eggs over twelve hours. The time-lapse videos were then uploaded to BORIS behavioral scoring software, where we scored the number and durations of invasions, cohabitations, attacks, courtships, and matings. We found many differences in behavior based on the sex of the intruder, as males invaded the nest more frequently and remained in closer proximity despite vigorous nest defense by the mother. Overall, we found that female intruders were much less aggressive than predicted, and that male persistence to return to the female’s shelter is key to receiving a high number of matings. Our study is the first to monitor these intimate interactions in the maritime earwig, and our results suggest that mothers may protect their eggs and appease male intruders by mating with them.