FLIGHT ORIENTATION OF DIABROTICA-VIRGIFERA-VIRGIFERA AND D-BARBERI (COLEOPTERA, CHRYSOMELIDAE) AT HABITAT INTERFACES

The short-range flight orientation behavior of adult western corn rootworms, Diabrotica virgifera virgifera LeConte, and adult northern com rootworms, D. barberi (Smith & Lawrence), was observed within plots of corn, Zea mays L. and soybean, Glycine max (L.) Merr., and at the interface between corn and other crop and noncrop habitats. The direction of flight was random within corn and soybeans, but at the interface between early- and late-planted corn, beetles of both species generally oriented more toward flowering corn than vegetative or post-flowering corn. Beetles also oriented toward corn rather than soybean, wheat (Triticum aestivum L.), and sweet clover (Melilotus officinalis (L.) Lam.) mixed with weeds, independent of the developmental stage of the corn. In general, flight orientation behavior did not differ with sex, and flight direction was not modified by wind or the presence of the observer. It appears that, although movement within a homogeneous habitat is random, movement at the boundaries of dissimilar habitats is nonrandom. This behavior should be considered in the development of models for predicting large-scale dispersal of these insects within the corn ecosystem.