Host-size preference of the parasitoidAnisopteromalus calandrae [Hym: Pteromalidae] onSitophilus zeamais (Col.: Curculionidae) larvae with a uniform age distribution

First generationAnisopteromalus calandrae (Howard) collected from commercial stored maize in South Carolina were exposed to a mixture of all sizes of immatureSitophilus zeamais Motschulsky, representative of a uniform age distribution, in shelled maize. Eighty-seven percent of parasitism is expected on larvae with tunnel diameters of 0.9 to 1.8 mm and 6% on prepupae and pupae, given this host-size distribution. Preference was greatest for large host larvae (1.6 mm diameter), intermediate for other larvae in the range 0.9 to 1.8 mm, and least for pupae and small larvae. Host-stage preference is discussed with respect to Chesson's (1983) parameters for preference, α_i, probability of parasitism, P_i, and electivity index, ?_i.