Abstract
Information on the life cycle of Euarestoides acutangulus (Thomson), including observations on feeding and reproductive behavior, is presented. The fly is bivoltine in central coastal California, with overwintering occurring as diapausing pupae. Eggs were laid in the staminate florets of the host plant, Ambrosia chamissonis (Lessing) Greene (Compositae), and hatched in 4 days. Larvae fed upon the anthers of unopened florets. The amount of damage caused to a staminate head depended upon the number of larvae reaching maturity and the number of florets within the head. Larvae generally completed development in 23 days. Pupation occurred among the destroyed florets. The pupal period of non-diapausing pupae required 12 days.