The question of whether “lake flies” bite is common, especially during mass emergence events near bodies of water. The insects most often given this common name are non-biting midges, and the answer is they do not bite and are entirely harmless to humans. While they resemble mosquitoes, the flies that emerge in huge swarms from lakes and ponds lack the biological equipment for piercing skin or drawing blood. They are considered a nuisance because of their sheer numbers, but they pose no threat of spreading disease or causing painful welts. These insects are an important part of the aquatic ecosystem.
Identifying the Non-Biting Midges
The flies commonly known as lake flies, bay flies, or “blind mosquitoes” belong to the family Chironomidae, which are classified as non-biting midges. They cause confusion because their slender bodies and long legs make them appear similar to true mosquitoes.
The primary structural distinction is the absence of an elongated, rigid proboscis, the specialized mouthpart mosquitoes use to pierce skin and feed on blood. Non-biting midges lack this piercing apparatus. Male midges are identified by their noticeably feathery, or plumose, antennae, which are much bushier than those of mosquitoes and help them detect mates.
Unlike mosquitoes, adult midges do not possess scales on their wings. When resting, many midge species hold their front pair of legs extended forward, a characteristic posture not typically seen in mosquitoes. Although their swarms are an annoyance, these physical traits confirm that the insects filling the air near lakes are not the blood-feeding variety. They are also distinct from other aquatic insects that emerge in large numbers, such as mayflies or the smaller, truly biting midges.
The Purpose of the Adult Stage
The reason adult non-biting midges do not bite is rooted in their compressed life cycle and biological purpose. The adult stage is dedicated almost entirely to reproduction, and for many species, their mouthparts are vestigial or greatly reduced. This means the adult fly is incapable of feeding on blood or solid food.
Their lifespan above water is short, often lasting only a few days, depending on the species and environmental conditions. During this brief window, their sole function is to mate and for the females to lay eggs back into the water. Some species do not feed at all as adults, relying entirely on the energy reserves accumulated during their aquatic larval stage.
The larval form, commonly known as bloodworms due to their reddish color, plays a different role in the ecosystem. These larvae live in the sediment at the bottom of the water body, where they feed on organic debris, algae, and detritus. They function as decomposers and recyclers of nutrients in the aquatic environment. The adult fly’s emergence marks the end of the feeding stage and the beginning of the reproductive stage, which has no need for a biting mechanism.
Managing Lake Fly Swarms
While lake flies do not bite, their tendency to emerge in massive swarms can create a nuisance, covering surfaces and accumulating around homes. Since the flies are a beneficial food source for fish, birds, and bats, non-chemical management strategies are the recommended approach. Reducing their presence is primarily achieved through light management, as adult midges are strongly attracted to bright outdoor lights.
Management strategies focus on reducing attraction and preventing entry:
- Replacing standard white outdoor light bulbs with yellow or amber-colored bulbs, as these colors are less visible to the insects.
- Using motion-activated lighting or turning off exterior lights after dark to prevent congregation near entry points.
- Ensuring all window and door screens are properly sealed to prevent the flies from entering the home.
For cleaning up the residue left by swarms, which can sometimes stain surfaces, hosing down the affected area with water is the best method. Wiping or smearing the accumulation can spread the residue and make the cleanup more difficult. Addressing the source of the problem, by reducing excessive organic matter like leaf litter and muck in the adjacent water body, can help limit the size of future hatches. These actions focus on minimizing the nuisance without harming the insects or disrupting the natural food chain.