DIURNAL CHANGES IN MICROHABITAT 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-degrees-C, 16 L-8D) and unregulated laboratories, and in field cages. Under laborato ry conditions the adult emergence from sweet potato tubers peaked in t he morning, whereas the feeding, mating and oviposition activity peake d at night. In the field cages the males were active on plants or on t he cage walls at night, while the females, being less active than male s during the hot season, tended to stay in the soil. In the cool seaso n, 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 durin g the hot season were more gravid than those from the plants. The sper matheca of females collected at night during the hot season in the soi l and in the tuber traps contained more sperm than those of females co llected on the plants. These results suggest that the males continue t o be active all night, whereas the females mate on the plants and then go subterranean for oviposition. This weevil is nocturnal with a pref erence for the shade.