Vertical Distribution of Adult Rice Weevils, Sitophilus oryzae L. (Coleoptera, Dryophthoridae), in a Stored Grain Bulk

Abstract

The results of an experimental study of the vertical distribution of Sitophilus oryzae L. adults in a 10-m high wheat grain bulk during storage are described. At the beginning of the experiment, the model grain bulk was infested with beetles at a uniform density of 5 ind. per 1 kg of grain. After 151 and 224 days of storage, live beetles were found only in the surface grain layer down to 0.1 m deep where their densities were 693 and 3943 ind./kg, respectively. At the same time, the densities of dead beetles in the grain bulk decreased considerably with depth.