Fig 1. Adult crane fly.
Some people think these flies look like Texas-sized mosquitoes! They have also wrongly been called “mosquito hawks”. Actually, mosquito hawks or “elephant mosquitoes” are true mosquitoes whose immature larval stages prey upon other mosquito larvae in their aquatic habitat. Scientifically, mosquito hawks are Toxorhychites species (Diptera: Culicidae). Crane flies belong to the fly family Tipulidae. There are about 1,458 species in the world and a number of these occur in Texas. Beginning mid-February, large numbers of adult flies emerge and rest on plants and walls outside the home (Fig. 1). However, species occur at normally low numbers throughout the year.
When the flies enter the home, they can become a nuisance. Crane flies do not bite or sting. In fact, they really do not feed. Their emergence, marking early spring, is their time for mating and seeking habitats to lay eggs for the next generation.
Larval farms of crane flies are grey-brown cylindrical larvae which may bear fleshy lobes on the back end (Fig. 2). Occasionally, the segments towards the front end of the body behind the head capsule can be greatly expanded.
Fig 2. Larval and pupal stages
Larval stages of crane flies in Texas feed primarily on decomposing organic matter. They commonly occur in moist environments such as woodlands and flood planes although some species inhabit open fields, dry rangeland and even desert environments. In central and east Texas they are often encountered under layers of decomposing leaves in wet locations such as ditch banks in December and January. In compost piles, they often occur on the soil surface below the pile of decaying vegetation. Although some species have been reported to feed on roots of forage crops or seedling field crops (Byers 1984), their presence here should cause little concern since they are assisting in the process of decomposition. Larvae have not been reported to feed on vegetable transplants or garden plants in Texas.
Management
Preventing adults from entering the home can be accomplished by assuring that window and door screens are in place and in good repair. Yellow-colored “bug lights” can be installed to keep from attracting as many flies as to conventional lights. Otherwise, merely leave outside lights off during evening hours. These practices will not completely eliminate these flies from being in or around the home, but they will reduce their numbers in these areas.
If the flies are in the homes, they can be swatted, vacuumed up or caught in a jar and removed to the outdoors. The main thing to remember is that crane flies are harmless and part of early spring in Texas. In fact, their biology is such that their contribution to our ecosystem is largely beneficial.
In Texas, larval or developmental stages are not know to be pests and, thus, do not need to be controlled. At best, larval habitats, such as piles of decomposing leaves and other organic materials can be removed or eliminated. However, in parts of Europe and Canada, one species of crane fly, Tipula paludosa, is known to be a pest of turf and pasture grasses and occasionally other crops because the immature stages feed on root hairs, roots and crowns of plants. This species is commonly called the ‘European crane fly’and the larval stages are called ‘leatherjackets’ (See “Leatherjackets in Ontario – What Gives!”, Ministry of Agriculture, Food and Rural Affairs, Ontario: http://www.omafra.gov.on.ca/english/crops/facts/turf_leather_may2198.htm).
Reference
Byers, G. W. 1984. Tipulidae (Chapter 24, pp. 491-514) in An Introduction to the Aquatic Insects, Second Ed. (R. W. Merrit and K. W. Cummins, ed.) Kendall/Hunt Pub. Co., Dubuque, IA, 722 pages.
Acknowledgment
This fact sheet is a minor revision of UC-022, last revised in April 1993.