Recently, I posted about adult male fruit flies imbibing alcohol after their courtship overtures were rejected by female fruit flies. Alcohol consumption is not confined to adult fruit flies. Immature fruit flies consume alcohol as well. Rotting fruit, the preferred food of fruit fly larvae, can contain up to 15 percent alcohol. Fruit fly larvae have robust enzyme systems for metabolizing the alcohol. This ability allows fruit flies to colonize rotting fruit that would kill insects that cannot handle the alcohol content.
Scientists at Emory University wondered if the alcohol could be of additional benefit to fruit fly health. Fruit flies can be attacked by parasitoid wasps. The parasitoids lay eggs inside the fruit fly larvae and the developing wasp larva consumes and kills the fruit fly. They placed fruit fly larvae in a divided dish. One side contained diet with 6 percent alcohol. The other side contained alcohol free diet. The results, published in Current Biology, conclusively demonstrate a detrimental effect of alcohol consumption by the fruit fly on a parasitoid wasp. None of the wasps were killed when the larvae fed on the alcohol free diet. About 60 percent of the wasps died when the fruit fly larvae fed on diet containing alcohol. Additionally, fruit flies parasitized by wasps preferred alcohol laced diet.
Diet of the host can have a major influence on parasitoid survival. There are many examples of wasps being killed when their insect hosts are feeding on toxic plants. It is not so surprising that alcohol consumption by the host could be detrimental to its parasites.