ENTFACT-500: Rat-Tailed Maggots and Moth Flies  |  Download PDF

by Lee Townsend, Extension Entomologist
University of Kentucky College of Agriculture 

Rat-tailed Maggots

The rattailed maggot is the immature or larval stage of a fly that resembles a honey bee. These 3/4 inch long whitish larvae are different from other fly maggots in having a 1/2 inch long "tail" that is used as a breathing tube when they are in the water. 

Large numbers can be present in most any accumulation of stagnant water, such as manure pits or lagoons, where they feed on decaying organic matter. The maggots become a nuisance when they crawl away from their breeding site to find a dry place where they can transform to the adult stage. In the wandering stage, hundreds of maggots may enter milking parlors, milk rooms, feed rooms, or other areas. They are harmless; small numbers can be swept up and thrown away. 

These tough-bodied larvae are usually not affected by even insecticides sprayed directly on them as they crawl along the ground. Insecticides are not easily absorbed through their thick covering. Placing a 4" to 6" wide, 3" deep barrier of dry, loose soil or sand in the path of the wandering maggots generally will stop them. They will burrow into loose, dry material and remain there. The soil and maggots can be shoveled up and discarded outdoors away from buildings. 

Rat-tailed maggots are seldom a problem in lagoons where:

• floating solids are kept to a minimum,
• the manure is completely covered with water deeper than the depth of the breathing tube, and
• banks are kept steep and free of emergent weed growth. 

Agitation of the pit contents or routine clean out, if practical, also can kill developing maggots. They can live in most any accumulation of shallow, stagnant water so keeping water from pooling around barns will reduce the number of breeding sites. 

Adults, called bee flies because of their resemblance to honey bees, are rarely seen. They do not remain around breeding sites like house flies do. Bee flies visit flowers for nectar but also will go to decaying odors where they may lay eggs. These flies neither bite nor sting and apparently do not carry diseases. 

Moth Flies

Moth flies are easily recognized by their speartip-shaped wings which are covered with scale-like hairs. The adults live for about 2 weeks. They are poor fliers and often accumulate on walls or vertical surfaces near breeding sites. They do not feed on humans or animals but can cause a sanitation problem in milk rooms. Moth flies swarm when disturbed and are small enough to pass through larger mesh window screens. 

The elongate larvae live in accumulations of stagnant water such as drain traps, wet manure, dirty garbage containers, septic tanks, and wet leaves. They have a grey body, a series of distinct dark bands across the back and a breathing tube at the end of the body. Development from egg to adult takes about 2 to 3 weeks. 

The adults can be killed by residual or pyrethrin space sprays that are used to control adult house flies. Solution of the problem requires that the breeding site be found and cleaned up or eliminated. Floor drains are a good starting place. Remove accumulations of muck in the drain and flush with scalding water. 

Revised: 05/94 

CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication. 

Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE! 

Images: University of Kentucky Entomology