Abstract: Summer diapause in cotton bollworm, Helicoverpa armigera(Hübner), is prolongation of the pupal stage, particularly in males, initiated by high temperature. Weight and weight loss of diapausing pupae and nondiapausing pupae exposed to high alternative temperatures of 33-39℃ were evaluated in the laboratory with normal developmental pupae from larvae reared at 27℃ as the control. In the experiment, pupation incidence at high temperature was significantly lower than that of the control; 63.2% of males and 10.9% of females fell into summer diapause when prepupae were exposed to alternative temperatures of 33-39℃. Weight of diapaused and nondiapaused pupae whose prepupae were exposed to high temperature was lighter than that of control pupae. Weight loss of pupae from 2nd to 5th day after pupation was less in diapausing pupae than those in nondiapausing and control pupae, I.e, 3.62, 13.30 and 5.49 mg respectively. The trend of total weight loss from pupation to emergence was similar to that from 2nd to 5th day after pupation, I.e., 15.60, 49.35 and 26.30 mg in diapausing, nondiapausing and control pupae, respectivley. The curves of weight loss of the three groups showed significant difference. The curve of diapausing pupae was relatively even and was located below the curves of nondiapaused and control pupae. However, when the diapausing pupae were placed at diapauseterminated temperature, the curve of their weight loss of pupae was similar to that of control pupae except longer duration in the former case because diapausing pupae had a period of response about 3 days to terminate diapause. The results indicate that with diapause pupae can reduce metoblism and delay their development under high temperature to survive adverse environment.

Key words: Helicoverpa armigera, high temperature, summer diapause, weight loss, weight loss curve