Larva is a maggot with coloration that can vary with combinations of gray, yellow, orange or green.
NY State Ag Experiment Station
The adult is a fly that mimics the coloration of wasps; it often hovers during flight (A). The eggs are white with a stippled sculptured surface (B). The larva (C) is a maggot of variable color (gray, yellow, orange, green or a combination of these colors). It is found among aphid colonies, often co-existing with other predators such as the gall midge. Note: Hover flies are sensitive to several broad-spectrum insecticides, especially the organophosphates.