Size Preference and Sex Ratio for Pteromalus cerealellae (Hymenoptera: Pteromalidae) Parasitizing Sitotroga cerealella (Lepidoptera: Gelechiidae) in Stored Corn

Abstract

Hosts ranging from small larvae to pupae of the Angoumois grain moth, Sitotroga cerealella (olivier), were exposed to females of the pteromalid parasitoid, Pteromalus cerealellae (Ashmead), to determine the effects of host size on preference, parasitism success, adult size, and progeny sex ratio of the parasitoid. The parasitoid successfully parasitized larvae (>0.43 mm in maximum body width), prepupae (1.55 ± 0.05 mm [mean ± SEM] mm maximum average body width), and a single pupa (1.20 mm maximum body width). All female parasitoid progeny emerged from hosts that had a maximum body width >0.85 mm. Sixty-four percent of male parasitoid progeny emerged from hosts that had a maximum body width between 0.43 and 0.85 mm. Size of P. cerealellae adults was correlated with host size (larger parasitoids developed on larger hosts). The optimal host sizes for producing female parasitoid progeny were larvae with a maximum body width between 1.69 and 2.05 mm and prepupae. The optimal host sizes for producing male parasitoid progeny were larvae with a maximum body width between 0.57 and 0.70 mm. These results are discussed in terms of maximizing potential biological control of the Angoumois grain moth by this parasitoid.