Diapause in the boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), remains a contentious issue despite intense investigation. In particular, the roles and interactions of photoperiod, temperature, and adult diet are poorly understood. We reexamined the influences of these factors by using a feeding regime typical of previous studies (group, one square per five weevils per day) as well as one known to promote reproductive development (single, one square per weevil per day). Three separate studies each incorporated all combinations of the following: photoperiod (short day, 11:13; long day 13:11 [L:D] h), temperature regime (constant 29.4°C; warm day, cool night, 29.4°C:10°C [day:night]), feeding regime, and age at dissection (3, 6, 9, and 12 d after adult eclosion). Studies differed in the source of weevils (Lower Rio Grande Valley, Brazos Valley of Texas), and the photoperiod used to rear weevils to adulthood (11:13 or 13:11 [L:D] h). Interpretable effects of photoperiod on diapause induction were not observed. Cool nights delayed development of fat bodies, oocytes with yolk, and the occurrence of diapause, especially in weevils fed in groups. However, these effects were not apparent by day 12. The most marked responses were to feeding regime. Hypertrophied fat bodies and diapause generally occurred more often, and oocytes with yolk less often, for weevils fed in groups compared with those fed singly. Fundamental differences in diapause response corresponding to rearing conditions or source of weevils were not observed. These results suggest improved understanding of the dynamics of adult diapause could be achieved through continued investigation of the effects of adult diets.
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Vol. 99 • No. 6