The appearance of large insect swarms can be alarming, leading many to fear a mosquito infestation; however, these gatherings often involve the non-biting insects commonly known as “blind mosquitoes.” These nuisance pests belong to the insect family Chironomidae, comprised of aquatic midges. Unlike true mosquitoes, blind mosquitoes do not possess the mouthparts necessary to bite, suck blood, or transmit diseases to humans or animals. The primary problem they present is their sheer number, as they emerge from water in massive swarms that create a significant localized nuisance and can cover exterior surfaces with their bodies.
Identifying Blind Mosquitoes
These insects are small and bear a superficial resemblance to true mosquitoes. A distinguishing feature is the male’s antennae, which are notably feathered or bushy, giving them the nickname “fuzzy bills”. Unlike mosquitoes, which hold their wings flat over their bodies at rest, blind mosquitoes often hold their wings tent-like over their backs. They also lack the scales on their wings that are characteristic of true mosquitoes.
Their life cycle is a four-stage process: egg, larva, pupa, and adult. The larval stage is entirely aquatic, living submerged in water and often burrowing into the mud and organic sediment. These larvae are commonly called “bloodworms” because their hemoglobin gives them a red color, allowing them to extract oxygen from low-oxygen aquatic environments. The adult stage is brief, lasting only a few days, and its sole purpose is mating and reproduction.
Locating the Source of the Infestation
The presence of swarming adult midges indicates that an aquatic breeding site is nearby, often within a mile of the nuisance area. These midges thrive in nutrient-rich water bodies, such as natural lakes, man-made storm water retention ponds, sewage oxidation ponds, and slow-moving ditches. High concentrations of organic matter and algae in these environments provide the primary food source for the developing larvae. Larval populations can reach extremely high densities in highly enriched habitats.
Adults are strongly attracted to exterior lighting. Adult midges are strongly phototactic, meaning they are drawn to light, which concentrates them around homes and buildings, especially after dusk. High-intensity lights, such as white light and mercury vapor bulbs, are particularly attractive to the swarms. This explains why the heaviest swarms often accumulate directly on the sides of light-colored buildings or around doorways and windows.
To locate the source, focus on any standing water within the immediate vicinity, including drainage ditches, ornamental ponds, and areas of consistently damp soil. Inspecting the bottom sediment of these water bodies for the presence of red “bloodworms” confirms the larval breeding location. Next, identify which exterior lights are attracting the largest concentrations of adults, as managing this light source significantly reduces the number of swarms congregating on the structure.
Immediate Control of Adult Swarms
Dealing with an active swarm of adult midges requires specific methods. One practical, non-chemical approach is to use a strong stream of water from a garden hose to physically knock down and disperse the swarms from walls and vegetation. For midges gathered near entryways, a vacuum cleaner with a hose attachment can quickly remove the resting insects. This prevents the accumulation of dead midges, which can leave stains and emit a fish-like odor as they decay.
The most effective immediate strategy involves modifying exterior lighting to reduce attraction. Switching standard white incandescent or fluorescent bulbs for yellow “bug lights,” or low-pressure sodium vapor lamps, significantly decreases the number of midges drawn to the area. These alternative light sources emit wavelengths less visible or attractive to the insects. Reducing the wattage of lights, shielding fixtures to direct light downward, or using motion detectors and timers to limit light-on time, are also effective measures.
Contact insecticides, such as those containing pyrethrins, can be used for quick knockdown of adult swarms. These chemicals are typically applied as a barrier treatment to vegetation and surfaces where the midges rest. However, this method is only a temporary solution, as the treated area will quickly be repopulated by new adults emerging from the aquatic source. Relying solely on adulticides does not address the root problem and can be counterproductive by killing natural predators.
Eliminating Larval Breeding Sites
Long-term control focuses on eliminating the larval “bloodworm” stage in the aquatic environment. Physical management involves reducing the organic sludge and sediment that the larvae feed on and inhabit. In small ornamental ponds or ditches, manually removing excess organic debris and sediment reduces larval density. For larger retention ponds, nutrient abatement strategies, such as managing landscape runoff, limit the excess nutrients that fuel algal growth, the larvae’s food source.
Aerating stagnant water bodies is another effective physical technique, as midge larvae often thrive in oxygen-depleted conditions. Introducing aeration devices, such as fountains or diffusers, increases the dissolved oxygen levels in the water. This makes the habitat less suitable for pollution-tolerant midge species and reduces the survival rate of the larvae.
Biological control involves introducing insectivorous fish, particularly bottom-feeding species like catfish or certain carp, into permanent water bodies to manage larval populations. These fish consume the midge larvae and pupae, although they may not always reduce the population below nuisance levels when larval numbers are extremely high.
Biological Larvicides
The most targeted control strategy involves using larvicides, which are products designed to kill the larvae before they emerge as adults. The biological insecticide Bacillus thuringiensis israelensis (Bti) is a highly recommended and environmentally conscious choice. Bti contains a protein toxin that specifically targets and kills the larvae of midges and mosquitoes when consumed, while remaining safe for fish, mammals, and other non-target organisms.
Chemical Larvicides
For effective control against midges, Bti must be applied at rates significantly higher than those used for mosquito larvae, as the midges feed on the bottom sediment, which can reduce the product’s effectiveness. Other chemical larvicides, such as insect growth regulators like methoprene, prevent the larvae from developing into adults. Their use requires caution and often a higher dose due to the larvae’s deep habitat in the sediment.