Effect of Temperature on the Termination of Prolonged Initial Diapause in Eobiana japonica (Bolivar)(Orthoptera : Tettigoniidae)

Eobiana japonica (formerly Metrioptera japonica) requires two or more years to complete its life cycle by entering diapause twice in the egg stage. Initial diapause occurs just after blastoderm formation and the final diapause shortly before hatching. The initial diapause lasted for more than a year in some eggs. The percentage of initial-diapause termination increased on the whole as the duration of exposure to 3℃ increased from 15 to 600 days. The intensity of initial diapause was considerably variable among individuals. Chilling longer than 600 days impaired the egg viability. Cold treatment was not indispensable to terminate the initial diapause because some or most eggs resumed development at constant temperatures between 15 and 30℃. Repeated exposure to low (90 days at 10℃ or 180 days at 3℃) and high temperatures (90 or 180 days at 25℃) was more effective than a single long cold treatment in terminating the initial diapause, and all the eggs resumed development after two or three such cycles.