Predatory earwigs, Euborellia annulipes, use guava volatiles to find shelter and fruit-fly prey

Euborellia annulipes, a nocturnal predatory earwig, has been found in association to fallen Myrtaceae fruits infested with fruit-fly larvae (Diptera: Tephritidae). Additionally, these fruits seem to serve as shelter for the earwigs, which deposit their eggs inside. Considering the importance of plant chemicals as cues for insects in their search for both prey and shelter, we hypothesized that volatiles from guava fruit (Psidium guajava) play these roles for the earwig E. annulipes. First, in arena tests, we investigated the role of guava fruits as shelters to earwigs by examining their preference for mechanically perforated guava fruits (MPF) or artificial fruits made from plastic (AF), as well as for MPF versus fruits infested with Ceratitis capitata larvae (IF), over a time course. Subsequently, we evaluated the earwigs’ attraction and preference for volatiles emitted from uninfested guavas (UF), MPF, or IF. The results of the arena tests showed that the earwigs preferred MPF over AF to shelter, but had no preference between MPF and IF up to 33 h; however, from 45 h after release, more females sheltered in MPF. The olfactory tests showed that the female earwigs recognized volatiles from MPF and IF, but preferred volatiles emitted by IF over those emitted by UF or MPF. Thus, our results suggest that females of E. annulipes use volatile chemical cues to locate guava fruits, which serve as shelter, and that despite being initially attracted by the odors of fruit-fly-infested guava fruits, they prefer to shelter in uninfested fruits after predation.