The influence of temperature on the post-diapausal development and survival in the aestivating eggs of Halotydeus destructor (Acari : Eupodidae)

Abstract

After diapause development is complete, moistened aestivating eggs of H. destructor develop successfully within the temperature range 5-20.5C. The rate of development up to the deutovum stage increases with temperature up to about 20C and then rapidly decreases. Eggs will tolerate temperatures between 25 and 31.5C for up to 53 days without undergoing morphogenesis, but this treatment retards subsequent development at 16C. Exposure to alternating temperatures accelerates the rate of development but, if the higher temperature exceeds 20.5C, development is retarded. The effect of temperature on the rate of development within the deutovum stage is similar to that on non-diapause winter eggs throughout their morphogenesis. Air-dry eggs will tolerate temperatures up to 75C but moist eggs are killed by exposure for 1 day to 45C. This high temperature tolerance, together with the limitations on development imposed by temperature, ensures that the aestivating eggs do not hatch before early autumn, even in the event of unseasonal summer rain. The temperature response curve and its ecological significance are discussed briefly.