Printed in Great Britain EGG DIAPAUSE IN EPHIPPIGER CRUCIGER (ORTHOPTERA: TETTIGONIIDAE) I. THE INCIDENCE, VARIABLE DURATION AND ELIMINATION OF THE INITIAL DIAPAUSE

Eggs of the bush-cricket Ephippiger cruciger may be subject to two periods of diapause during the course of embryogenesis. After oviposition not all eggs develop at temperatures favourable to morphogenesis, some cease activity at the unsegmented embryonic primordium stage. If these eggs are cooled for 10-30 days some develop on subsequent exposure to higher temperatures, but further prolongation of the cooling period does not render more eggs com-petent to develop. Although cooling for longer than the critical period does not affect the proportion of eggs which subsequently start to develop, it does affect the time within which reactivated eggs begin to develop. The delay in the initiation of development after cooling increases with the duration of the chilling period. Excessively long cooling periods, however, impair the eggs' ability to complete embryogenesis. It is evident that eggs laid in one season will develop and hatch over a number of years