Diel activity patterns of the squash bug egg parasitoid Gryon pennsylvanicum (Hymenoptera: Scelionidae)

Abstract

Mated, 1-d-old female Gryon pennsylvanicum (Ashmead) exhibit a diel pattern of activity and rest. Daily activity (e.g., oviposition, walking, grooming, flying, feeding) is greatest during morning hours (0815-1215 hours CST). Two forms of resting behavior occur. “Motionless“ is a temporary state occurring mostly during afternoon hours. The more pronounced resting phase, “tucking,“ occurs in aggregated individuals of both sexes and is a form of rest previously undescribed in the parasitic Hymenoptera. The period of tucking persists from before lights go off to about 1 h after the lights go on. In individual wasps, activity resumes abruptly at about 0830 hours; by 0930 hours, all adults become active. Observations of a field population show a similar pattern of diel activity. The significance of these data for biological control programs is discussed.