Diapause in the aestivating egg of Halotydeus destructor (Acari : Eupodidae)

Abstract

The occurrence of an aestivating diapause in the eggs of the red-legged earth mite, H. destructor, is established. The production of diapause eggs in females is influenced by the increasing maturity of food plants in the spring. Morphogenesis is resumed following exposure to early summer conditions for 4-6 weeks in the field. In the laboratory, diapause development was achieved by exposing the eggs to various combinations of temperature and relative humidity. The most effective treatment was exposure for 32 days to 52DC and 50% R.H., although diapause development occurred within the temperature range 15-70DC and relative humidity range 10-100%, and even when the eggs were completely immersed in water. It was most successfully promoted in atmospheres having vapour pressures of about 40 mmHg, at all temperature and humidity combinations. At 20% R.H., diapause development was relatively slower than at humidities above and below this, whereas tolerance to high temperatures was greatest at this humidity. Diapause eggs were not harmed either by complete immersion in water or by periodical desiccation and re-moistening.