Suitability of three Ostrinia species as hosts for Macrocentrus cingulum: a comparison of their encapsulation abilities.

Two cornborer species, Ostrinia furnacalis (Lepidoptera: Crambidae) and O. nubilalis, are major corn pests in Asia and Europe, respectively. In both continents, the larval endoparasitoid Macrocentrus cingulum (Hymenoptera: Braconidae) develops on another, closely related stemborer, O. scapulalis, which feeds on mugwort and other dicotyledons. M. cingulum also emerges from O. furnacalis in Asia and O. nubilalis in North America, but not from O. nubilalis in Europe. We assessed the ability of three populations of each of the three Ostrinia species to encapsulate foreign bodies of a size similar to that of a M. cingulum egg. We conclude that variations in encapsulation ability alone cannot account for the differences observed in the field between parasite emergence rates in these different host species and geographic areas.