Midge

Midges of the family Chironomidae are among the most abundant and widely distributed insects on Earth, with larvae found in nearly every type of freshwater habitat, from clean mountain lakes to low-oxygen ponds and even brackish water. Despite their mosquito-like appearance, adult midges do not bite and have no functional mouthparts for feeding.

The larvae, often called bloodworms for the reddish hemoglobin that lets them survive in oxygen-poor sediment, are a foundational part of aquatic food webs, providing food for fish, amphibians, and countless invertebrates. Their tolerance of pollution and low oxygen also makes certain species useful indicators of water quality.

Adult midges are best known for the large mating swarms they form, often over water or nearby structures at dusk, a spectacle that can appear as a shimmering column of insects and is sometimes mistaken for a cloud of biting mosquitoes.

• Slender, mosquito-like body 2-10 mm long, but without scales on the wings
• No piercing mouthparts; adults cannot bite
• Males have distinctive plumose (feathery) antennae used to detect the wingbeat frequency of females in swarms
• Front legs often held forward or upward when perched
• Body color ranges from pale green to tan, brown, or black depending on species
• Lookalikes: mosquitoes have scaled wings, a piercing proboscis, and a more upright resting posture, while midges lack both the proboscis and wing scales

Midges occur worldwide near still or slow-flowing freshwater such as ponds, lakes, marshes, and rivers, with larvae living in the bottom sediment or attached to submerged vegetation. Some species tolerate highly polluted or low-oxygen water where few other insects can survive. Adults typically stay close to their natal water body, forming swarms nearby, especially at dusk in warm months.

Adult midges generally do not feed at all and live only a few days, devoting their brief adult life to forming large mating swarms, often visible as a hovering column over a landmark such as a bush or rooftop. These swarms and the larvae in the sediment below serve as a critical food source for fish, birds, bats, dragonflies, and spiders. Larvae are detritivores, feeding on algae, bacteria, and organic particles within the sediment, and some construct small silk-lined tubes for shelter.

Females lay eggs in a gelatinous mass on the water surface, which sinks and releases larvae into the sediment below. Larvae pass through four instars while feeding on organic material, a process that can take from a few weeks to several months depending on temperature and species. Pupation occurs within the sediment or a silk tube, after which the pupa rises to the surface and the winged adult emerges. Many species produce multiple generations per year in warm conditions, while others overwinter as larvae in colder climates.