Ecophysiology and adaptive behaviour of earwigs
Principal Investigator: Matthias W. Lorenz
The European earwig (Forficula auricularia) is a common species in Europe and North America. In late autumn, males and females enter the ground and mate. When oviposition starts, males are usually forced out of the nest by the female and die. The females stay below ground and care for their eggs. During this long hypogaeic phase, which lasts from late October to early April, females do not consume any food. Therefore, adult females face a considerable trade-off between egg production and survival of the hypogaeic period: during summer and early autumn adult females not only have to provide energy to fuel vitellogenesis but also need to fill their fat body stores for later use during the prolonged phase of starvation. Using field populations, we investigate the energy allocation in adult females and attempt to explain the underlying regulatory mechanisms.
Male earwigs use their forceps as weapons in intrasexual competition and for intersexual signalling. In laboratory experiments, male size and the size of the forceps have been identified by several authors as the major traits enabling successful reproduction. One interesting facet of our field work on earwigs is the fact that in late October/early November no females but still some males can be found foraging above ground – i.e. males which obviously haven’t found a mate. According to our preliminary results, these males are mostly brachylabic, whereas only few macrolabic males are present above ground in late fall. Thus, our field observations support those lab studies which demonstrated that females preferably choose males with long forceps as their mates.