Influence of Host Age on Patch Use by a Quasi-Gregarious Egg Parasitoid

Abstract

Abstract In quasi-gregarious egg parasitoids, the effects of host age on patch use can be significant because host quality declines with host age; this occurs simultaneously in all hosts in a patch (i.e., egg mass). We assessed such effects in the laboratory using Gryon obesum Masner, an egg parasitoid of Euschistus conspersus Uhler. Host eggs hatched ≈6 d after oviposition; therefore, individual parasitoid females were allowed to oviposit on egg masses (14 eggs/mass) of 0-, 1-, 2-, 3-, 4-, and 5-d-old hosts. We measured body size and developmental time of parasitoid progeny from these hosts. On egg masses of 0-, 2-, 4-, and 5-d-old hosts, we observed ovipositional behavior of parasitoid wasps, and estimated rates of host acceptance, progeny survival, and patch residence time. There was a general decline in host quality with host age. Exposure of wasps to 5-d-old hosts resulted in reduced percentage parasitism, lowered acceptance and ovipositional success per patch, increased patch time, reduced survival ...