Syrphid Fly - Toxomerus politus
Order Diptera | Family Syrphidae - Flower Flies, Hover Flies

Live adult Syrphid fly photographed in the wild at northern Illinois, USA.
Insects & Spiders | Flies Index | Tachinidae | Dung Flies | Bee Flies | Robber Flies
The hover flies are a large group of generally beneficial insects. Their coloring and movements of most species mimic bees or wasps -- they are either stout-bodied and covered with hair, resembling a bumble bee, or boldly patterned with yellow, orange and black, resembling wasps or honey bees. Some species even go so far as to wave their front legs in front of their face to mimic the jointed antennae of the potter wasps. Adult hover flies can generally be found hovering in midair or feeding at flower blossoms. They eat only nectar and pollen. However, their larvae can be rapacious predators of aphids, thrips, and mites, or parasitic in the nests of ants or solitary bees. Still other larvae scavenge in soil or decaying plant material or eat living plants. Some are aquatic.

Syrphid flies are routinely used as a biological control in the lettuce fields of California's vegetable-producing regions, where the fly's larvae are generally effective in controlling lettuce aphid (Nasonovia ribisnigri). It is primarily the Syrphidae that enable organic romaine growers on California's central coast to produce harvestable crops.

Syrphidae larvae are, in turn, parasitized by wasps in the Hymenoptera families Ichneumonidae and Pteromalidae [1].

Syrphidae Head Detail

Most hover flies are between 5-20 mm long, brightly colored in yellow and black, and have large compound eyes that nearly cover the head. One rule of thumb for identifying hover fly gender is if the eyes meet at the top of the head, it's a male specimen. Each wing has a characteristic fold, or "false vein" which can be visible to the naked eye - it is located anterior to the first large vein that runs all the way to the outer margin of the wing. Of course, being true flies, they have only one pair of wings, plus the characteristic halteres, or bulb-like organs that evolved from the second pair of flying wings.
Syrphid Fly - Toxomerus politus
The blue bands on this syrphid fly's abdomen are an unusual color in this family.
References
  1. University of California, DANR, "Biological Control Agents for Aphids in Vegetable Crops"
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Flies of North America - Order Diptera. Flies are prevalent in virtually all habitats, with over 16,000 species in North America. Flies can be distinguished from all other insects in that they only have one pair of normal wings. Most flies have compound eyes and mouthparts adapted for piercing, lapping or sucking fluids.
Syrphidae | Flies Index | Tachinidae | Bee Flies | Robber Flies
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