Migration and the effect of three environmental factors on the pre-reproductive period of the cotton-bollworm moth, Helicoverpa armigera
Migration by noctuid moths generally occurs while the adults are sexually immature, and so the pre-reproductive period provides an indication of the time available for migratory flight. Helicoverpa armigera (Hb.) (Lepidoptera: Noctuidae) is considered to be a facultative migrant, emigrating in response to a deterioration in local environmental conditions for adult survival and larval development; hence the effects of temperature, vapour-pressure deficit and the availability of sugar solution on the duration of the pre-reproductive period are investigated. Temperatures below 28oC lengthened female pre-reproductive periods but, contrary to the findings of Isley (1935) for Helicoverpa zea (Boddie), temperatures above 28oC shortened them. Females maintained at a vapour-pressure deficit of 23.7 ± 0.5 mmHg (c. 12% r.h.) and 6.45 ±0.15mmHg (c. 76% r.h.) did not have significantly different pre-reproductive period distributions. The availability of 10% w/v sugar solution (provided ad libitum) had a marked effect on both the survival and the pre-reproductive period of both sexes. Moths given water for four nights followed by sugar solution thereafter, took significantly longer to reach reproductive maturity than those given sugar solution from emergence. Survival to reproductive maturity of moths given water only throughout their lives was poor (c. 20%). The significance of these findings to the migratory behaviour of H. armigera is discussed.
Colvin, J.; Gatehouse, G. Migration and the effect of three environmental factors on the pre-reproductive period of the cotton-bollworm moth, Helicoverpa armigera. Physiological Entomology (1993) 18 (2) 109-113. [DOI: 10.1111/j.1365-3032.1993.tb00456.x]