THE ROLE OF VISION IN THE HOST PLANT-FINDING BEHAVIOR OF THE HESSIAN FLY

After mating, female Hessian flies, Mayetiola destructor (Say), sit for several hours before taking flight and exhibiting host-finding behaviours. Observation of these behaviours indicated that females used both chemical and visual cues to find oviposition sites, and that visual cues from plants consisted of both spectral (colour) and spatial information. Females oriented to and were stimulated to land on targets reflecting wavelengths in the region of 530-560 nm (either alone or in combination with UV) but were inhibited by wavelengths from 400 to 500 nm. This spectral discrimination was probably mediated by photoreceptors located in the medio-frontal zone of the compound eyes. The spatial patterning of targets also influenced orientation during flight; targets with vertical rather than horizontal contour lengths and a higher density of vertical contour lengths were approached and landed on more frequently.