High temperature induced diapause in the cotton bollworm Helicoverpa armigera

In laboratory studies, Helicoverpa armigera (Hubner) (Lep. Noctuidae) from Burkina Faso exhibited pupal dormancy induced by high temperatures. Exposure to 37 degrees C from the 3rd larval stage caused 94.7% of males to diapause but only 60.9% of females. No influence of daylength (12 and 16 h) was observed. Induction by high temperatures must begin during the larval stage to be effective. The pupal stage is not sensitive to induction. After storage at 37 degrees C for 60 days, 64.3% of dormant pupae survived and most of them resulted in adult emergence. After storage at 37 degrees C for 85 days, no dormant pupae survived. The development of dormant pupae is resumed after about 20 days at 21 degrees C whatever the duration of prior exposure to 37 degrees C (7, 14 or 30 days). There is no delay in non-dormant pupae kept at 21 degrees C. The possible role of this 'hot thermal diapause' in the life history of H. armigera in Burkina Faso is discussed.