Photoperiodic Induction of Reproductive Diapause in the Predators Nabis americoferus and Nabis roseipennis (Heteroptera: Nabidae)

Author： YEARGAN K. V. BARNEY W. E.

Publisher： Entomological Society of America

ISSN： 1938-2901

Source： Annals of the Entomological Society of America, Vol.89, Iss.1, 1996-01, pp. : 70-74

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Abstract

The predators Nabis americoferus (Carayon) and N. roseipennis Reuter are common in several agroecosystems and overwinter as adults. Studying females, we found that the critical photoperiod for induction of reproductive diapause at 24°C is between 13.5 and 14.0 h light per day for both species. To determine the stage most sensitive to diapause inducing photoperiods, pairs of cohorts were reared to various points in their development under a photoperiod of 15 h light per day (not diapause inducing) or a photoperiod of 11 h light per day (diapause inducing) and then reciprocally switched to the opposite photoperiod for the remainder of development. Fewer than 10% of the individuals entered diapause when switched from the not diapause inducing to the diapause inducing photoperiod at the beginning of the adult stage. In contrast, when individuals were moved from the not diapause inducing to the diapause inducing photoperiod at the beginning of the 5th stadium, 78.4% of the N. americoferus and 87.5% of the N. roseipennis entered reproductive diapause as adults. When either species was switched from the not diapause inducing to the diapause inducing photoperiod at the beginning of any earlier stadium, 100% of the cohort entered reproductive diapause as adults. Thus, the nymphal stage is the most sensitive to diapause inducing photoperiods. Reciprocal switches from the diapause inducing to the not diapause inducing photoperiod showed that the adult stage must continue to experience a short photophase for diapause to occur. Once the critical photoperiod is reached during late summer in the field, of course, individuals will experience diapause inducing photoperiods for the remainder of their development.