Gnat Life Cycle

Image of a Gnat

How Long Do Gnats Live?

A gnat is a small two-winged fly. They can either be biting or non-biting and typically form large swarms of adults. These small flies are holometabolis, which means they develop in four stages – egg, larva, pupa, and adult. The following small flies fit the above description.

  • Fruit flies
  • Phorid flies
  • Fungus gnats
  • Eye gnats
  • Black flies
  • Biting midges

  • Fruit Flies

    Image of a Fruit Fly

    Fruit flies are known for their ability to reproduce rapidly and in large numbers. Their preferred habitat is moist areas that contain organic matter and damaged or overripe fruits.

    The process from egg to adult takes about 7 days. Adults live for about 10-25 days, depending on environment and available food. Female fruit flies lay several batches of eggs and are ready to mate about two days after becoming adults.

    About 24 hours before adults emerge from the pupal case, the pupa forces its way out. Within about two days, the new adults are ready to breed and begin a new generation.

    Phorid flies

    Image of a Phorid fly

    Phorid flies are sometimes called sewer flies, since they are frequently associated with leaking or clogged drains and sewer pipes. Also known as hump-back flies, these pests can take about 11-22 days to complete their life cycle.

    The immature stages of phorid flies live in the organic matter that is found in drains. They will develop in contaminated soil under broken sewer pipes. Females produce about 500 eggs in a lifetime.

    Fungus gnats

    fungus gnat image

    These small flies live in gardens and over-watered houseplants. Mold and other microorganisms that grow in moist soil and decaying plant debris are this insect’s main food source. Fungus gnat swarms can annoy residents, with larval stage feeding damaging plant roots over time.

    About three days after an adult female deposits eggs, they hatch and larvae emerge. The larval stage lasts about 10 days before reaching the pupal stage. Pupae develop into adulta after about 4 days. In total, a new generation of fungus gnats can appear every 17 days.

    Eye gnats

    These gnats are members of the genus Liohippelates. Breeding and developmental sites are locations with well-drained soils and abundant organic matter. Eye gnats feed on perspiration or fluids associated with the eyes, nose, mouth, ears, and open wounds.

    The life cycle can range from 11 days to three months depending on conditions like temperature and moisture. Development from egg to adult is completed in about three weeks. In the southern parts of the U.S. there are multiple generations each year.

    Black flies

    Image of a Black Fly

    Black flies, also known as buffalo gnats and turkey gnats, are small flies that bite wildlife, livestock, and humans. Some species produce only one generation per year, but most bring forth several generations annually.

    Females lay batches of up to 450 eggs in running water or on aquatic plants. Larvae require around 4-30 days to hatch.

    Larval development typically takes about two weeks. For black fly species that overwinter as larvae, development may extend from the fall until spring.

    What Do Black Fly Larvae Eat?
    Larvae feed on small organisms and debris found in the water.

    Some black fly species remain in the pupal stage for only 2-6 days, while others take as long as 3-4 weeks.

    How Long Do Black Flies Live?
    When emerging from the pupal case, adults float to the stream’s surface in an air bubble and quickly fly away. Adult black flies typically live for a few weeks. Most black fly species mate in swarms, while some actually reproduce on the ground. Black flies feed on nectar, and females must consume a blood meal for proper egg development.

    Biting midges

    Depending on factors such as species and environment, the biting midge life cycle takes about 2-6 weeks. Adults are mostly found near breeding sites but will sometimes disperse to mate.

    Males typically emerge from their pupal case before the females. Mating often occurs in flight when females fly into swarms of males. Other midge species reproduce without swarming. Instead, the males find hosts on which females consume blood, and mating occurs after feeding.

    The number of eggs produced varies by species. Biting midges lay batches of about 25-100 eggs near salt marsh and mangrove swamps. Eggs may also be found at the edges of streams and ponds.

    Larvae & Adults
    After hatching, biting midges spend about 2 weeks or more in the larval stage. The pupal stage is generally very short, only lasting 2-3 days. The lifetime of adults varies, but generally adults live for only a few weeks.