Active from spring through autumn, females lay fertilized eggs on plants and the larvae feed on aphids, small caterpillars and other soft-bodied insects they encounter. Larvae look like green worms with a yellowish coloring down the middle and a thin dark line along the 'back'. They are well camouflaged for the green foliage they live on. So efficient and hungry are these larvae that they may completely eliminate a population of aphids off of a plant by harvest time. Adults drink nectar and may be seen visiting flowers.
References: University of California-Davis Department of Agriculture and Natural Resources (publication #8285); Field Guide to Insects of North America by Kaufman