The term “gnat” is a common name used to describe numerous species of small, winged flies within the insect order Diptera, not a precise scientific classification. These minute insects are usually encountered indoors or near moist areas. They can be non-biting or biting, depending on the species. Identifying these pests helps determine the source of an infestation, as different types of gnats breed in distinct environments.
The General Appearance of Gnats
Most insects commonly referred to as gnats share several physical characteristics. Adult gnats are very small, generally measuring between 1/16 and 1/8 of an inch (1.5 to 3 millimeters) long. Their bodies are slender and elongated, often appearing dark gray or black.
The insect’s body has three main parts, and their six legs are long and spindly relative to their small size. Gnats possess a single pair of functional, usually translucent wings with visible veining. When flying, they exhibit a weak, erratic, or fluttering flight pattern, often hovering in small clusters or clouds.
Visual Differences Between Common Household Gnats
Distinguishing between common household gnats requires focusing on specific visual cues, as many are similar in size. The Fungus Gnat, frequently found near houseplants, has a slender, mosquito-like body and long legs. These insects are weak fliers and tend to run across surfaces rather than flying when disturbed.
Drain Flies, also known as Moth Flies, have a distinctly different appearance. They have short, hairy bodies that give them a fuzzy, moth-like look. Their wings are covered in fine hairs and are held in a roof-like or heart shape over the body when at rest. They are found around sink drains and other areas with standing water and decaying organic film.
The Fruit Fly is often misidentified as a gnat but is stouter and more compact than the slender Fungus Gnat. The most common species are tan to brownish-yellow and possess distinct, bright red eyes. Phorid Flies, sometimes mistaken for gnats, have a hump-backed or barrel-shaped thorax and prefer to run or “scuttle” rapidly across surfaces rather than taking flight.
What Gnat Larvae Look Like
Identifying the larval stage provides definitive evidence of the infestation source, since adults only indicate the presence of a breeding site. Gnat larvae are legless and worm-like, with elongated, segmented bodies that are often whitish or translucent. They are found within the moist substrate where the adult female laid her eggs, such as damp potting soil or decaying matter.
Fungus Gnat larvae, which are common, can grow up to a quarter-inch long. Their most distinctive feature is a shiny black head capsule at one end of the pale body. These larvae move through the soil by a wiggling motion and are found close to the surface in the top inch of moist material.