Black flies are small, dark-colored insects often encountered in outdoor environments, particularly near flowing water.
Overall Appearance and Size
Black flies are generally small insects, typically measuring between 1 to 5 millimeters in length. Their body shape is notably stout and robust, often described as having a characteristic arched or “humpbacked” appearance, especially noticeable in females. This distinctive shape has led to their common name, “buffalo gnat.”
The coloration of black flies usually ranges from black or dark gray to brownish. Some species can also appear yellowish or even orange. Despite these color variations, they maintain a compact and sturdy overall look.
Specific Body Features
Their wings are broad and fan-shaped, typically appearing clear or slightly smoky. These wings feature prominent veins, particularly along the leading edge, and usually rest over the body when the fly is at rest.
Black flies possess short and thick antennae, which are composed of 9 to 11 segments. Their legs are also short and stout, contributing to their compact build.
The head of a black fly features large, round compound eyes. In males, these eyes may meet at the top of the head.
Their mouthparts are short and adapted for piercing and sucking. While their function involves blood feeding in females, their physical presence as a proboscis is a visual attribute.
Distinguishing Them from Other Insects
Mosquitoes, gnats, and fruit flies are frequently confused with black flies.
Mosquitoes generally have a more slender body shape compared to the stout black fly. Their wings are narrower and often covered in scales, unlike the broad, clear wings of black flies. When at rest, mosquitoes tend to stand on their long, delicate legs with their bodies held parallel to the surface, a posture distinct from the more compact black fly.
Gnats, particularly non-biting gnats, often appear more delicate than black flies. While some gnats are also dark-colored, they typically have longer, dangling legs and more slender bodies. Fungus gnats, for example, have long, narrow wings that can seem disproportionately large for their bodies.
Fruit flies are usually tan or brown, and many species possess distinctive bright red eyes, which are a strong identifying feature. Their bodies are generally rounder than the humpbacked profile of a black fly, and their wings may exhibit unique patterns or spots.