The locomotor activity of Cryptolestes ferrugineus (Stephens) (Coleoptera:Cucujidae) in wheat

Abstract

Moisture content was the factor that most affected locomotor activity of Cryptolestes ferrugineus in wheat at 15°, 22°, and 28 °C. More insects emigrated from dry than from damp wheat; accelerated emigration from damp wheat after 4 days at 28° was attributed to the growth of storage fungi, primarily Aspergillus spp. and Penicillium spp. Emigration was not different at insect densities ranging from 5 to 50 insects per 98 g of wheat.C. ferrugineus was positively geotactic except in wheat which had been previously infested. Emigration was stimulated in daylight and by continuous illumination, but was depressed in darkness.Starved insects were less active than unstarved insects in dry wheat, but both groups were equally active in damp wheat. Insects were more active in dry than in damp wheat, but activity did not differ when both wheats were cracked to provide more accessible feeding sites. Locomotor activity in moldy wheat was related to preconditioning; more insects preconditioned for 3 days in dry wheat remained in moldy wheat than did those preconditioned for 3 days on damp wheat.The results suggest that insects concentrate in damp or cracked wheat because they can feed, oviposit, and develop more readily than is possible in dry wheat. Thus, in grain bulks C. ferrugineus tends to disperse in dry regions and to concentrate in moister regions.