Syrphid Flies
Order: Diptera
Family: Syrphidae
Description
Syrphid flies, commonly referred to as hover flies, are brightly colored yellow or orange flies with black markings that mimic bees or yellow jackets. However, syrphid flies are harmless to people. Syrphid flies are slender, typically 4-25 mm (1/8-1 inch) in length and have one pair of wings. The eggs are elongated, slightly curved, around 1 mm (1/25 inch) in length, and found near food sources for larvae such as aphid colonies.
The larvae are light colored with varying shades of white, green, tan, or brown and often have strips, small bumps, or spikes. They are maggots with bodies that taper at the ends and lack an external head capsule. After hatching, larvae are about 1.5 mm (1/16 inch) long. When mature, they measure about 1.3 cm (1/2 inch) long. Pupation occurs on vegetation, bark, or a stationary object. The teardrop or bulb shaped pupae have a leathery texture, small bumps at the rear, and measure about 1.3 cm (1/2 inch) in length.
Quick Facts
- Syrphids flies mimic bees and wasps as an anti-predation. However, they can be identified by their slender abdomen and short antennae.
- The larvae of syrphid flies feed on various insect pests, while adults feed on pollen and nectar.
- Eggs are laid individually on plants, usually near prey.
- Keeping flowering plants in the garden will attract adults. When possible, the use of broad-spectrum insecticides should be avoided since they are toxic to syrphid flies.
Adult syrphid fly feeding on a flower. Image credits: Whitney Cranshaw, Colorado State University, Bugwood.org
Adult syrphid fly. Note the slender abdomen and short antennae. Image credit: Jeremy Lee, Bugwood.org
Larva of syrphid fly near an aphid colony. Image credits: Whitney Cranshaw, Colorado State University, Bugwood.org
Syrphid fly pupa. Note the tear drop shape and bumps at the rear. Image credit: David Cappaert, Bugwood.org
Syrphid fly (right) next to a yellow jacket (left). Note the shorter antennae on the syrphid fly. Image credit: Frank E French, Georgia Southern University, Bugwood.org
Life history and habits
Syrphid flies have four life stages: egg, larva, pupa, and adult. The larvae molt three times, getting larger with each instar before pupating. Syrphids typically overwinter in protected areas as prepupae. After emerging as adults, females mate and lay eggs near aphid colonies or other small, soft-bodied insects. The larvae are active predators that begin feeding after they hatch. A single syrphid fly larva can consume over 100 aphids throughout its development. One or more generations can be produced each year, depending on the species.
Conservation
Reducing the use of broad-spectrum insecticides helps conserve syrphid flies and their larvae, improving long-term control of insect pests.
Planting suitable habitats can provide syrphid flies with shelter and prey for larvae. Flowers preferred by syrphid flies include aster, buttercup, mustard, carnation, rose, and parsley. Such plantings can be especially beneficial early in the season before pests become abundant.
References
Price, S., and R. Patterson. 2019. Beneficial Predators: Syrphid Flies. Utah State University – Extension. Available https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=2969&context=extension_curall#:~:text=Syrphid%20flies%20are%20common%20residents,home%20landscapes%20providing%20pollination%20services.&text=Larvae%20of%20syrphid%20flies%20are,providing%20naturally%20occurring%20pest%20control.
Schuh, M. 2022. Syrphid flies. University of Minnesota – Extension. Available https://extension.umn.edu/beneficial-insects/syrphid-flies
UCANR. (n.d.). Syrphids (Flower Flies, or Hover Flies). University of California – Agriculture and Natural Resources. Available https://ipm.ucanr.edu/natural-enemies/syrphids/