Survival, morphological, physiological, and reproductive changes in overwintering boll weevils, Anthonomus grandis grandis Boheman, in the Lower Rio Grande Valley of Texas were studied. The number of boll weevils captured per trap declined significantly from the postharvest period to the beginning of the spring over two overwintering seasons: 2000-2001 and 2001-2002. The proportion of males and females trapped did not differ significantly. Ninety percent of captured weevils died within 47.6 days when fed, while 90% of unfed weevils died after 9.0 days. This trend was not affected by month of capture. Female weevil fat body ratings were significantly greater at the beginning of fall than in the spring, while most male weevils from September through March were rated as lean (82.5-100%). No differences in male reproductive parameters were observed in those captured during the cotton free-period compared with the middle of growing cotton season (June), except for testes size which was larger during the latter period. The percentage of females with oocytes in their ovarioles, and the percentage containing oocytes with yolk, were significantly lower in September than in June. During October-March, we did not observe any females with chorionated eggs, whereas in June 96% females contained them. We found that weevil females can oviposit eggs in the Lower Rio Grande Valley during the overwintering period after feeding 7-20 days on a reproductive diet of cotton squares. Females captured later in the winter fed at longer period before laying eggs.