Distribution of C ryptolestes ferrugineus (Coleoptera: Cucujidae) in response to temperature gradients in stored wheat

Abstract

Temperature gradients were established in a 56 cm diameter cylinder with 9 cm high sides filled with 19.9 kg of hard red winter wheat to determine if adult rusty grain beetle, Cryptolestes ferrugineus (Stephens), would disperse to warmer areas. C. ferrugineus moved into and remained in warmer areas of the grain mass after 24 h. Beetle preference for the warmest area of the grain mass occurred at 21–20°C, 24–20°C, and 42–20°C temperature gradients. No preference was shown for any area of the grain mass when no gradient was established. The beetles were able to locate the warmest area even at the 21–20°C gradient. In autumn, grain stored in bins cools fastest on the outside of the bulk and remains warmer longer in the center. This study suggests that C. ferrugineus should move toward the warmer center region of a grain mass as the periphery of the grain cools in the fall. This would allow C. ferrugineus populations to continue to increase in the center of the grain mass during the winter months in large, unaerated, grain bins.