The stable fly is about the size of a house fly but is dark gray and has dark irregular spots on its abdomen. The proboscis (mouthpart) protrudes bayonet-like in front of the head. The larvae are typical whitish fly maggots. The pupae are chestnut brown and about 1/4 inch long.
Life History
The complete life cycle of the fly from egg to adult can take 14-24 days in Nebraska during hot weather. The overwintering part of the stable fly life cycle may not be completely known. Some do overwinter below the frost line as slowly developing larvae. As temperatures rise, the larvae move toward the soil surface and pupate, and these pupae give rise to at least some of the adults of the first generation of the season. There is some speculation that part of the first generation migrates from the south each spring. Stable flies are capable of moving considerable distances, but no documentation shows that a migration occurs.
The female fly deposits eggs in spoiled or fermenting organic matter mixed with animal manure moisture and dirt. The most common breeding sites are in feedlots or dairy lots, usually around feedbunks, along the edges of feeding aprons, under fences and along stacks of hay, alfalfa and straw. Grass clippings and poorly managed compost piles also may be stable fly breeding areas.
The most common breeding areas outside of the lots are the drainage areas leading to holding ponds. The drainage channels should have a slope of at least 3 inches. This slope allows rapid drainage and prevents wet areas within the drainage channel from becoming a fly breeding area. The ponds themselves, if properly designed and maintained, do not provide a fly breeding area. Slopes should be steep, not filled with solids and must be kept clean of weeds. If fly breeding is occurring at the edge of the drainage channels and irrigation water is available, the channel can be flooded to drown the flies.
Each female fly lives about 10 to 30 days and lays 100 to 400 eggs during her lifetime. In warmer areas the stable fly may breed all year.
Source: John B. Campbell, Extension Entomologist, University Of Nebraska