EFFECT OF TEMPERATURE ON THE TERMINATION OF DIAPAUSE IN THE UNIVOLTINE ALMOND SEED WASP EURYTOMA-AMYGDALI

Diapausing larvae of Eurytoma amygdali Enderlein (Hymenoptera, Eurytom idae) were collected in early August and late September. They were sub jected to various photoperiod and temperature regimens for up to 20 we eks, then kept at L16:D8 and 19 degrees C for another 14 to 26 weeks f or diapause to be terminated and pupation to take place. Photoperiod d id not affect diapause completion. It was confirmed that the two morph ologically distinct diapause stages have different temperature require ments for their completion. The first diapause stage was completed syn chronously at temperatures between 16 and 19 degrees C. A higher tempe rature of 26 degrees C delayed diapause development. The second stage required lower temperatures between 4 and 10 degrees C. Spontaneous te rmination of diapause was observed at constant 19 degrees C. When appl ied to the first diapause stage for 20 weeks, low temperatures made th e larvae refractory to subsequent intermediate temperatures. The first stage was thus maintained until a higher temperature of 26 degrees C made the larvae regain their ability to respond to the intermediate te mperatures and complete this stage. Larvae grown in Retsou almonds had a higher diapause intensity than larvae grown in Truoito almonds. The results suggest that, in nature, the high temperatures of late summer and early autumn are likely to maintain the first diapause stage. Sub sequently, the less warm temperatures of autumn allow the completion o f the first stage by late autumn, and the low temperatures of late aut umn and of winter allow the completion of the second diapause stage by mid winter.