Earwig × Fruit fly × Parasitoid: Interactions
Description
The earwig Euborellia annulipes (Dermaptera: Anisolabididae) is a generalist predator. It was recently observed in fruits infested with fruit flies, whose juveniles are frequently attacked by parasitoid wasps. However, the predation of these fruit flies by E. annulipes has not yet been recorded nor has their intraguild interaction with parasitoid wasps. In this study, we explored earwig-fruit fly-parasitoid interactions using the E. annulipes earwig, the Mediterranean fly Ceratitis capitata (Diptera: Tephritidae), and the parasitoid wasp Diachasmimorpha longicaudata (Hymenoptera: Braconidae). We hypothesized that (1) earwig adults prey on fruit fly larvae and pupae, and this predation depends on the earwig sex and prey density and developmental stage; (2) earwigs are able to recognize and avoid parasitized prey; and (3) chemical markings on the host left by the parasitoid are recognized by the earwigs. In laboratory experiments, earwig females and males preyed on second and third-instar larvae and pupae of C. capitata, and females predated more than males regardless of the stage of development of the prey. Predation was higher in second-instar larvae, followed by third-instar larvae and, finally, fruit fly pupae. Females and males exhibited a type II functional response. Males killed but did not consume their prey more than females, effectively contributing to the elimination of prey even when they were not consumed. In no-choice tests, parasitized and nonparasitized fruit fly larvae were consumed by adult female earwigs in similar proportions. However, in choice tests, the female earwigs avoided feeding on parasitized larvae. Subsequent tests indicated that the parasitized larvae were recognized by semiochemicals released by the parasitoids during parasitism of the larvae. This result indicates that this earwig has the ability to identify parasitized prey and prefers to avoid intraguild predation. These findings are unprecedented and indicate that E. annulipes has the potential for biological control of C. capitata and that by avoiding intraguild predation, this earwig will have an additive effect on pest mortality.