Ovipositional Response of Indianmeal Moth (Lepidoptera: Pyralidae) to Size, Quality, and Number of Food Patches
2006
Nansen, C. | Meikle, W.G. | Phillips, T.W.
Indianmeal moth, Plodia interpunctella (Hubner), is one of the most important pests in retail stores and processed food facilities, but little is known about its ovipositional response to varying sizes and qualities of food sources. In this study, we monitored oviposition for 48 hours divided into 16 consecutive 3-h intervals, and found that, on average, P. interpunctella females laid eggs 6.4 times. We found a positive correlation between number of oviposition events and total oviposition. We conducted laboratory experiments to examine the distribution of eggs laid by P. interpunctella females in dishes that varied in size and number. Experiments were conducted with “improved” food (cracked or walnut oil-treated wheat kernels) and “control” food (plain untreated wheat kernels). In trials with dishes of two different sizes, P. interpunctella females seemed to distribute eggs according to the surface area of dishes regardless of the food. In trials with improved food, total oviposition was positively associated with the number of dishes, whereas the number of control dishes had no apparent effect on total oviposition. In trials with one improved food dish and one to eight control food dishes, P. interpunctella females consistently preferred oil-treated wheat kernels, whereas they showed no preference for cracked wheat kernels. Using an index of randomness (D(p)), we demonstrated that the distribution of eggs was significantly different from a Poisson distribution, thus indicating that it was nonrandom, regardless of the number of dishes. Using an index of aggregation (Im2), we showed that for all the foods, the distribution of eggs became increasingly aggregated with higher numbers of dishes and that this trend was most pronounced in trials with improved foods.
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