Temperature as a sole factor for diapause induction after pupation in Helicoverpa zea (Lepidoptera: Noctuidae)
1992
Pullen, S.R. | Meola, R.W. | Lopez, J.D. Jr
When Helicoverpa zea (Boddie) was reared in a diapause-averting photoperiodic (14:10 [L:D] h) regimen at 26 degrees C, placed at 15 degrees C within 24 h of larval-pupal ecdysis, and kept at 15 degrees C for at least 14 wk, approximately 45% of the insects entered a state of dormancy. Sixty-five percent of these dormant pupae were males. Evidence that this dormant state was similar to temperature-photoperiodically induced diapause was provided by the following three observations: (1) dormant pupae maintained for 15 wk at 15 degrees C required the same number of days to initiate adult development at 26 degrees C as H. zea in a temperature-photoperiodically induced state of pupal diapause, (2) females required significantly fewer days than males to initiate adult development, and (3) injection of 20-hydroxyecdysone elicited a similar low percentage of diapause termination in 10-wk-old temperature induced dormant and temperature-photoperiodically induced diapausing pupae. Based on these results, it is postulated that temperature-induced diapause in newly formed pupae may serve as a secondary diapause induction mechanism to assure species survival.
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