DISTRIBUTION OF CRYPTOLESTES-FERRUGINEUS (COLEOPTERA, CUCUJIDAE) IN RESPONSE TO TEMPERATURE-GRADIENTS IN STORED WHEAT

Temperature gradients were established in a 56 cm diameter cylinder wi th 9 cm high sides filled with 19.9 kg of hard red winter wheat to det ermine if adult rusty grain beetle, Cryptolestes ferrugineus (Stephens ), would disperse to warmer areas. C. ferrugineus moved into and remai ned in warmer areas of the grain mass after 24 h, Beetle preference fo r the warmest area of the grain mass occurred at 21-20 degrees C, 24-2 0 degrees C, and 42-20 degrees C temperature gradients. No preference was shown for any area of the grain mass where no gradient was establi shed, The beetles were able to locate the warmest area even at the 21- 20 degrees C gradient. In autumn, grain stored in bins cools fastest o n the outside of the bulk and remains warmer longer in the center. Thi s study suggests that C. ferrugineus should move toward the warmer cen ter region of a grain mass as the periphery of the grain cools in the fall, This would allow C. ferrugineus populations to continue to incre ase in the center of the grain mass during the winter months in large, unaerated, grain bins. Published by Elsevier Science Ltd.