Effect of Relative Humidity on the Developmental Stages of Tribolium castaneum (Coleoptera: Tenebrionidae)1

The life cycle of the red flour beetle, Tribolium castaneum (Herbst), was studied under controlled conditions of 30°C and 40°C temperature, and 70% and 90% relative humidity. At the higher humidity, metabolism of the larvae seemed to be accelerated, resulting in rapid development, while the eggs and pupae were unaffected. The eggs exhibited greater activity at 40°C than at 30°C, with consequent reduction in their incubation period. Larvae and pupae failed to survive at 40 °C. Therefore, the eggs of T. castaneum appear to have a good water-regulating mechanism and a higher thermal tolerance than the larvae and pupae.