TEMPERATURE-GRADIENT ON TRIBOLIUM-CASTANEUM (COLEOPTERA, TENEBRIONIDAE) ADULT DISPERSAL IN STORED WHEAT

The dispersal behavior of Tribolium castaneum (Herbst) adults along a 22-36 degrees C temperature gradient in stored wheat was monitored ove r a 20-h period with 8 microphones. Males tended to disperse more read ily than females but both preferred temperatures of >30 degrees C. Sin gle adults generally did not stay at one location very long, and the a verage time of 9.7 min spent at the warm end with a temperature gradie nt was longer than that of 4.4 min spent at that location without a te mperature gradient. An adult moved to a location 1, 2, and 3 microphon es (7.8, 15.6, and 23.4 cm) away from where they were previously detec ted in 88.2, 10.6, and 1.2% of the cases. The temperature preference w as much more evident with groups of 6 adults than with single adults b ecause the presence of other adults apparently increased the time that adults spent at preferred temperatures. Observations on the times spe nt at different temperatures, the distances mol ed, and the influence of the sex of an adult and the presence of other adults provide the in formation needed to develop a predictive model for adult dispersal in response to the temperature gradients that occur in stored grain durin g the autumn and spring.