Cuticular hydrocarbons of adult Pteromalus cerealellae (Hymenoptera : Pteromalidae) and two larval hosts, angoumois grain moth (Lepidoptera : Gelechiidae) and cowpea weevil (Coleptera : Bruchidae)

The pteromalid parasitoid Pteromalus cerealellae (Ashmead) is nominally a h ost-specific ectoparasitoid of the stored-product pest the Angoumois grain moth. It is readily cultured, however, on a number of other stored-product pests, including the cowpea weevil. The parasitoids,resulting: from these d ifferent hosts are disparate in size, leading me to ask if the cuticular hy drocarbons of P. cerealellae reared on different hosts would be different. This question is of importance because many parasitoids of stored-product p ests use cuticular hydrocarbons as major species- and gender-recognition cu es, and moth and beetle hosts differ greatly in their hydrocarbon profiles. The parasitoid hydrocarbon profile reported here was much more complex tha n the profiles of either either host and showed both gender and host effect s. Parasitoids reared on the larger cowpea weevils were larger than those r eared on moths and contained substantially more hydrocarbon on their cuticl e. Regardless of host, female wasps were always larger than males and conta ined more hydrocarbon than males. The hydrocarbon chemistry of wasps Feared on different hosts were qualitatively the same, but quantitatively differe nt. Both gender and host are important in the relative abundance of individ ual hydrocarbons. There are four major hydrocarbons of females constituting 49% of the total female profile: 3-MeC29, 11-MeC31, 3, 7-DiMeC(31) and 11, 17-, 11, 19- and 11, 21-DiMeC(33). There is one major male-specific hydroc arbon comprising 18% of the total hydrocarbons, 3, 7- and 3, 9 -DiMeC(33). Although major gender differences occur between hydrocarbon classes, these differences are not host-related.