Ohio’s Natural Enemies: Long-Legged Flies

Order Diptera, Family Dolichopodidae
ENT-69
Agriculture and Natural Resources
Date: 
01/15/2016
Andrea Kautz, Department of Entomology
Mary M. Gardiner, Department of Entomology

Despite having a generally poor reputation, flies are a large and diverse order of insects with a diversity of feeding habits. This generally misunderstood group includes many species that are actually beneficial because of the pest control or pollination services they provide within farm fields and gardens. The long-legged flies are just one such group of “good flies” found commonly in Ohio landscapes. Long-legged fly larvae and adults are predators that feed on a variety of soft-bodied arthropods. They do not bite and pose no threat to humans.

Role in Biological Control

Long-legged flies are predators and are therefore considered beneficial to have around for pest control. They have been known to feed on a rather wide variety of other small arthropods, including other flies, thrips, aphids, mites, springtails, leafhoppers, whiteflies, beetle larvae, and even termites! They will carry their prey around with them in flight as they secrete digestive enzymes into it and ingest the liquefied contents (similar to spiders). 

Identification

Long-legged flies (Figure 1) are small (1-9 mm), but easy to recognize because of their metallic green, blue or gold coloration, slender body shape, and not surprisingly, rather long legs! Often you can find them scurrying about on vegetation in the sunlight during the day. They are excellent fliers, but usually run or fly short distances from leaf to leaf when disturbed, making them a lot of fun to observe in your own backyard!

There are thousands of species of long-legged flies found worldwide and many found in the state of Ohio, so they can vary widely in body size and other characteristics. For example, some species have black spots or bands on the wings, while others have completely transparent wings (Figure 1). Also, males often possess secondary sexual characteristics that are used in complex courtship behaviors, such as flags on the front legs or modified antennae (Figure 2). Genera most commonly found in Ohio agroecosystems include Chrysotus (Figure 1e) and Condylostylus (Figure 1b and 1c).

 
Figure 1

A: Dolichopus. 

B: Condylostylus. 

C: Condylostylus. 

D: Medetera.

E: Chrysotus. 

F: Plagioneurus. 
Long-legged flies range in size from 1 to 9 mm and are usually a shining metallic color ranging from green to blue to bronze. They are generally characterized by their slender body and long legs.

Life Cycle

Figure 2
Two male long-legged flies showing examples of specialized body features used in courtship: flags on the front legs (left) and modified antennae (right).

Long-legged flies reside in a wide variety of habitats, with different species occurring in forests, grasslands, wetlands and agroecosystems. Flies undergo complete metamorphosis, which means they have distinct egg, larval, pupal and adult stages. Adult females typically lay their eggs in moist soils, or in some cases under the bark of trees. The larvae are predators, feeding on soil- or bark-dwelling invertebrates, and the pupae are also found in the soil (Figure 3). Most likely, you won’t encounter long-legged flies until they reach their adult stage. The adults are sensitive to cold temperatures so you will typically only see them after the last frost in the spring up until the first frost in the fall.

Mating behavior in adults is complex and often involves elaborate displays by the male to attract a nearby female (Figure 4). If you are lucky, you may be able to witness some of these fascinating behaviors yourself!

Be sure to also check out other Ohio State University beneficial fly fact sheets about hover flies and tachinid flies!

 
Figure 3 Figure 4
A long-legged fly larvae (left) and pupa (right), both of which reside in the soil or under bark but are not commonly encountered. A mating pair of long-legged flies (left) and another male (right) attempting to court the same female by waving his ornamented front legs for her.
References
  • Bickel, D.J. 2009. Dolichopodidae (Long-legged Flies). In: Brown, B.V., Borkent, A., Cumming, J.M., Wood, D.M., Woodley, N.E., Zumbado, M.A. (Eds.), Manual of Central American Diptera, Volume 1, NRC Research Press, Ottawa, Ontario, Canada: 671-694.
  • Kautz, A.R. 2015. Local Management and Landscape Effects on the Predator Guild in Vegetable Crops, with a Focus on Long-legged Flies (Diptera: Dolichopodidae). Master’s thesis. The Ohio State University. (Accession No.  OSU1437474798).
  • Pollet, M., S.E. Brooks, J.M. Cumming. 2004. Catalog of the Dolichopodidae (Diptera) of America North of Mexico. Bulletin of the American Museum of Natural History 283, 1-114.
  • Robinson, H., J.R. Vockeroth. 1981. Dolichopodidae. In: McAlpine, J.F., Peterson, B.V., Shewell, G.E., Teskey, H.J., Vockeroth, J.R. and Wood, D.M. (eds.), Manual of Nearctic Diptera. Volume 1. Agriculture Canada Monograph 27: 625-639.
  • Ulrich, H. 2004. Predation by adult Dolichopodidae (Diptera): A review of literature with an annotated prey-predator list. Studia Dipterologica 11: 369-403.
Photo​ Credits

Figure 1APhoto courtesy of Tom Murray (Creative Commons); Figure 1BPhoto courtesy of Andrea Kautz; Figure 1CPhoto courtesy of Steve Nanz (Creative Commons); Figure 1D Photo courtesy of A. Jaszlics (Creative Commons); Figure 1EPhoto courtesy of Steve Nanz (Creative Commons); Figure 1FPhoto courtesy of Lord Zimlich (Creative Commons); Figure 2Photos courtesy of Andrea Kautz; Figure 3, leftPhoto courtesy of Jiri Hulcr (Creative Commons); Figure 3, rightPhoto courtesy of Gerald J. Lenhard (Creative Commons); Figure 4Photo courtesy of Steve Marshall (with permission).

Program Area(s): 
Ohioline http://ohioline.osu.edu