Functional response and progeny production of the Madeira mealybug parasitoid, Anagyrus sp. nov. nr. sinope: The effect of host stage preference

Abstract

Anagyrus sp. nov. nr. sinope Noyes & Menezes (Hymenoptera: Encyrtidae) is a koinobiont parasitoid with an oviposition preference for the third-instar and pre-reproductive adult female Madeira mealybug, Phenacoccus madeirensis Green (Hemiptera: Pseudococcidae). In this study, we report that host stage preference significantly influenced the parasitoid's functional response and progeny production. The parasitoids exhibited a type II functional response when offered either second-instar or pre-reproductive adult female P. madeirensis at densities of 2-70 mealybugs per patch. The number of mealybugs parasitized within a 24-h period increased with host density up to the estimated maximum of 13 adults and 28 second-instar nymphs. The total number of progeny produced was higher from adult mealybugs and increased with host density until threshold densities (20 adults or 30 second-instar nymphs per patch) were reached. The maximum number of progeny produced in both host stages over a 24-h period was limited by the daily egg load, which was on average 23. Brood size was consistently higher in adult mealybugs and at higher host densities. The proportion of males decreased with an increase in host density and was higher when emerging from the adult mealybugs. Brood size and sex ratio of Anagyrus sp. nov. nr. sinope were similar at higher host densities, suggesting that there was a critical density after which the parasitoids only deposited a fixed brood size or sex ratio. © 2007 Elsevier Inc. All rights reserved.