Diurnal activity patterns of Colaspis brunnea (F.) and Colaspis crinicornis Schaeffer (Coleoptera: Chrysomelidae)

Grape colaspis, Colaspis brunnea (F.) (Coleoptera: Chrysomelidae), is a major pest of rice, Oryza stativa L., and an occasional pest of corn, Zea mays L., and soybean, Glycine max (L.) Merr. in the United States. Colaspis crinicornis Schaeffer has been becoming abundant in corn and soybean in recent years in some parts of the Great Plains. Diurnal activity patters of these two Colaspis species were studied. A sweep net was used to sample in soybean fields and prairies, and whole plant counts were performed in cornfields. Although beetles were collected in sweeping throughout the sampling periods, higher numbers of beetles were generally captured at night for both species. In cornfields more beetles were active at night than during the day; most beetles stayed in the whorl and at the base of leaves during the day while they tended to feed, mate, and move more at night. Understanding diurnal activity patterns of these species may be important when sampling them to determine their population densities in the field.