While there is some variation surrounding what insects constitute as gnats, this article will address only those small flies that are non-biters and are likely to be pests within homes and other structures. This includes fruit flies, fungus gnats, phorid flies and moth flies.
The breeding and developmental sites for these small flies are varied, but for the most part include habitats that stay moist and contain decomposing waste components. Control of these gnats generally centers on removal of their egg laying and feeding sites.
Where Do Gnats Lay Eggs?
The gnat’s life cycle’s first developmental stage is the egg, and subsequent developmental stages are the larvae, pupae and finally the adult. Gnat eggs are extremely small and rarely seen without the aid of a good hand lens or dissecting microscope.
Female gnats that have mated with a male will lay their eggs in hidden, out of the way locations either in or extremely close to their development habitats that consist of moist areas containing decomposing, fermenting products and waste components. Specifically, female gnats lay their eggs in the following habitats:
Fruit fly lay eggs under or one the surface of fresh and decomposing fruits and vegetables, plus the surface of locations where moist, organic debris is allowed to accumulate. Specific egg laying sites include dirty drain lines, poorly cleaned garbage disposals and garbage cans, recycle containers or other places where “organic slime” is allowed to accumulate. In addition, other areas can include cracks and crevices of kitchen equipment, crevices where floors and walls intersect and mops or brooms that contain food debris or other organic materials. The fruit fly egg stage is around for only about 30 hours before the larval stage begins its development.
Fungus gnat lay eggs in moist soil or moist organic debris of plant origin. Some examples of habitat where females lay eggs include piles of leaves, garden and grass debris, compost piles and mulch. It takes about three days before the larval stage hatches from the eggs.
Phorid fly lay eggs in places such as decaying animal carcasses, drain pipes, places where wastes have leaked onto the ground from damaged sewer lines, dirty garbage cans and other trash containers. In fact, most pest management professionals think that phorid flies have the most diverse developmental sites of any fly species. Females lay somewhere near 40 eggs and larvae emerge about one day after eggs are laid.
Moth fly females lay eggs in drains, sewage plants and on the “slime” from dirty waste containers. Eggs hatch in about one and a half to two days.
This article would not be complete without describing the effect a phorid fly in the genus Pseudacteon has on fire ants. These female flies are known to deposit their eggs in the thorax of fire ants. When the fly’s egg stage is complete, larval phorid flies move to the head of the fire ant and begin feeding on the tissues in the ant’s head.
After the fly larva completely eats the ant’s brain, the ant becomes a “zombie” and wanders about purposelessly until its head falls off and the fly pupates in the separated head, soon after developing into a mature adult fly.