Biting midges, also known as “no-see-ums” or “punkies,” are tiny, blood-feeding flies. Their minuscule size often makes them go unnoticed until their painful bite is felt, making their identification challenging.
Key Physical Features
Adult biting midges are remarkably small, typically measuring 1 to 3 millimeters in length, about the size of a pencil point or pinhead. This minute stature allows them to easily pass through standard window screens, making them both indoor and outdoor pests. They are generally grayish, dark brown, or black, though a blood-fed female’s body can appear reddish-brown.
They have a short, stocky body with a humped thorax and a tapered, nine-segmented abdomen. Their two wings often display dark patterns or blotches. When at rest, these wings are held flat and crossed over their abdomen, resembling closed scissors. Their wings are typically shorter than or equal to their body length.
Their antennae are segmented, commonly having 15 segments. Males have feathery antennae, while females’ are smoother. Biting midges have specialized piercing-sucking mouthparts. These short, less noticeable mouthparts contain a fleshy sheath with tiny cutting blades that lacerate the skin. This cutting action, akin to a “jigsaw power tool,” causes the immediate, sharp pain of their bite.
Distinguishing from Other Small Insects
Differentiating biting midges from other small flying insects, such as mosquitoes or gnats, requires observing key visual and behavioral distinctions. Biting midges are considerably smaller than most mosquitoes, measuring 1 to 3 millimeters compared to a mosquito’s typical 3 to 6 millimeters. This size disparity makes them difficult to spot before they bite.
Wing characteristics also offer clear differentiation. Biting midge wings often display distinct dark patterns. In contrast, mosquitoes generally have longer wings that extend past their body and are covered with scales, giving them a fringed appearance. When at rest, biting midges typically hold their patterned wings flat and crossed over their body, and they may hold their front legs forward and upward. Mosquitoes, however, tend to rest with a more humpback posture and often hold their hind legs outward and upward.
The mouthparts of these insects also vary. Biting midges have short, cutting mouthparts that slice into the skin, causing an immediate, sharp sensation. Mosquitoes, conversely, have a long, needle-like proboscis that pierces the skin, with bites often felt later. While both cause itchy welts, their initial sensation and bite mechanism differ.
Biting midges are generally not known to transmit diseases to humans in North America, though some species can transmit pathogens to livestock. Mosquitoes, however, are well-known vectors for various human diseases.
In terms of behavior, biting midges often fly slowly and form dense swarms, unlike faster-flying mosquitoes that do not form such concentrated groups. While the term “gnat” is a broad classification, biting midges are sometimes specifically referred to as “biting gnats,” distinguishing them from non-biting midges or other small flies.