Diurnal changes in micro-habitat usage and behavior of Cylas formicarius (Fabricius)(Coleoptera: Curculionidae) adults

Diurnal changes in micro-habitat usage by Cylas formicarius adults and of their behavior therein were studied in regulated (27°C, 16L-8D) and unregulated laboratories, and in field cages. Under laboratory conditions the adult emergence from sweet potato tubers peaked in the morning, whereas the feeding, mating and oviposition activity peaked at night. In the field cages the males were active on the cage walls at night, while the females, being less active than males during the hot season, tended to stay in the soil. In the cool season, both sexes tended to stay in the soil or on its surface, and their activities declined. Mating and flying occurred at night. The females collected in the soil and from sweet potato tuber traps at night during the hot season were more gravid than those from the plants. The spermatheca of females collected at night during the hot season in the soil and in the tuber traps contained more sperm than those of females collected on the plants. These results suggest that the males continue to be active all night, whereas the females mate on the plants and then go subterranean for oviposition. This weevil is nocturnal with a preference for the shade.