A method of population control for a diapausing race of Teleogryllus commodus, based on the introduction of a non-diapausing population, is postulated. One factor that could influence the degree of probability of success of the method is the susceptibility of eggs of the northern tropical race to winter temperatures when exposed to the temperate climate of the south. Tests were conducted which showed that eggs of the tropical race were more vulnerable to low temperature and had a higher threshold of development. Hybrid eggs appear to be intermediate in their ability to survive low temperature. A comparison of the diapausing characteristics of races from widely separated localities in Australia confirmed the non-diapausing characteristic of northern Queensland races; all others showed the ability to enter diapause but varied in the proportion of eggs in which diapause was averted by exposure to high temperature. A method of rearing crickets, suitable for the production of large numbers for field release, is described.