Factors potentially affecting oviposition site selection by the lady beetle Coleomegilla maculata (Coleoptera: Coccinellidae)

Coleomegilla maculata (DeGeer), a polyphagous lady beetle, is one of the most common predators in corn fields in the eastern United States. Previous work on C. maculata showed an oviposition preference for the weed Acalypha ostryaefolia Riddell (hophornbeam copperleaf), compared with three other weed species and corn. In a separate field study, we found far more C. maculata eggs on Abutilon theophrasti Medic (velvetleaf) than on eight other plant species. Here we report on studies designed to assess the potential roles that prey densities and weed attractiveness may play in the selection of oviposition sites by C. maculata. We also examined diurnal and nocturnal predation of C. maculata eggs on Zea mays L., A. ostryaefolia, A. theophrasti, and Amaranthus hybridus L. (pigweed). We found that C. maculata's choice of plants on which to oviposit was not significantly influenced by the availability of potential prey on those plants. There was no difference in the number of C. maculata adults captured on sticky traps placed over preferred weeds, nonpreferred weeds, or bare soil, suggesting that oviposition choices are made after the beetles land on plants. Coleomegilla maculata egg clusters on A. theophrasti and A. ostryaefolia were preyed upon less frequently than clusters on A. hybridus and corn, indicating that A. theophrasti and A. ostryaefolia provide refuge from predation (including cannibalism) of C. maculata eggs. Unlike the other plant species tested, both A. theophrasti and A. ostryaefolia possess numerous glandular trichomes, which may reduce foraging activity of potential predators of C. maculata eggs on those plants.