Notes on floral resource utilization in two sympatric earwig species (Dermaptera: Forficulidae)

Abstract

The Dermaptera (earwigs) are widely known to the public but have been much less documented in the literature as a taxon of anthophilous insects. Here, we report on the floral utilization of two sympatric earwig species, Forficula mikado and Anechura harmandi, from summer to autumn on Rebun Island, Hokkaido, Japan. Both the nymphs and adults utilized diverse plant taxa (36 species from 15 families) as either foraging or resting sites. They often utilized flowers of the Asteraceae (15 species) and/or Apiaceae (5 species) as foraging sites, probably because of their easily accessible, exposed pollen. In A. harmandi, both nymphs and adults primarily foraged on asteraceous flowers. However, in F. mikado, nymphs frequently utilized apiaceous flowers, whereas adults primarily exploited asteraceous flowers. This ontogenetic dietary shift may be explained by an innate preference of F. mikado nymphs for apiaceous flowers rather than competition for floral resources between F. mikado and A. harmandi nymphs, because flower-visiting earwigs were not so abundant on the island.