Abstract
The eggs of GryUulus commodus, if incubated at high temperature (26.8°C.), soon after laying, did not develop and hatch promptly. Instead hatching was spread over a long period and many eggs died. If the eggs were given a period of exposure to low temperature (12.8°C.) before incubation at high temperature,· prompt hatching occurred. This was due to diapause, which occurred at an early stage in the morphological development of the egg.