The term “gnat” is a common, non-scientific label applied to various tiny, flying insects. Their small size and tendency to swarm make them noticeable pests. When people ask if gnats are insects, the answer is unequivocally yes. “Gnat” serves as a convenient umbrella term for multiple species of small flies that share common features like minute size and presence in human environments.
The Scientific Answer
Gnats are classified within the Class Insecta, possessing the defining features of all true insects: a segmented body divided into a head, thorax, and abdomen, and six jointed legs. More specifically, gnats belong to the Order Diptera, which translates to “two wings” and includes all true flies, such as house flies and mosquitoes. This order is characterized by having only a single pair of functional wings attached to the thorax.
The second pair of wings is reduced to small, club-shaped balancing organs called halteres, which are used for stabilization during flight. Gnats typically fall into the suborder Nematocera, which features species with delicate bodies and long, segmented antennae.
Common Types of Gnats
The common name “gnat” is a catch-all for several distinct families of small flies, each with a unique habitat preference. The most frequent indoor nuisance is the Fungus Gnat (family Sciaridae), which is associated with houseplants and damp soil. These are weak flyers, often seen walking or hopping across the potting mix surface.
Another common type is the Drain Fly (family Psychodidae), also known as a moth fly, which has a fuzzy, moth-like appearance. These flies breed in the gelatinous, organic film that accumulates inside plumbing and sewer drains.
Finally, the outdoor pest often called a gnat is the Biting Midge (family Ceratopogonidae), commonly known as a “no-see-um” because of its minute size. Only the female biting midge requires a blood meal for egg development, delivering a painful bite compared to its size.
Understanding Reproduction and Habitat
The persistent presence of gnats is related to their rapid life cycle and dependence on moist, decaying organic matter. All gnat species undergo complete metamorphosis, progressing through four stages: egg, larva, pupa, and adult. The entire life cycle can be completed in as little as 17 to 25 days under warm and humid conditions, allowing for multiple overlapping generations.
The larval stage is the primary feeding stage and requires a constant source of moisture and organic material. Fungus gnat larvae feed on fungi and plant roots in saturated soil, while drain fly larvae consume the biofilm sludge found in pipes. Adult gnats are generally short-lived and exist mainly to mate and lay eggs, making control efforts focused on the flying stage largely ineffective.
Management and Elimination Strategies
Effective gnat control relies on eliminating the larval breeding source to interrupt the reproductive cycle. For fungus gnats, modify the environment by allowing the top two inches of potting soil to dry completely between waterings. This practice removes the fungi and moisture necessary for the larvae to survive. Sticky traps can monitor and capture the adults, but they do not solve the root problem.
To eliminate drain flies, the organic sludge lining the drain must be physically removed using a stiff brush or pipe cleaner. Enzymatic drain cleaners are more effective than bleach or boiling water, as they break down organic matter and target the film where the larvae feed.
Controlling biting midges, which develop in wet mud, salt marshes, or moist decaying vegetation, involves eliminating areas of standing water and reducing organic debris near residences.