Flower Fly (Toxomerus marginatus)
Detailing the identifying qualities of the Flower Fly, including physical features and territorial reach.
Updated: 8/4/2017; Authored By Staff Writer; Content ©www.InsectIdentification.org
Flower Flies in the Toxomerus genus look like wasps, giving them a bit of peace while they scour plants for aphids and other plant pests.
Seeing this Flower Fly in the garden is a win. Not only is it harmless to people, it helps clear vegetable and fruit plants of insects that drain and damage them. They are keen mimics of wasps with similar colors and banding on the abdomen, but a look at the eyes and antennae reveal what they really are. In this species, female eyes are separated (see photo), while male eyes are smashed right next to each other (holoptic).
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