The brine fly, a small insect belonging to the genus Ephydra, often gathers in immense numbers around highly mineralized bodies of water. The concern is understandable, given the sheer size of the swarms they form. The answer to the most common question about these insects is straightforward: no, brine flies do not bite.
The Direct Answer: Do Brine Flies Bite?
Adult brine flies lack the necessary mouthparts to pierce skin or draw blood. Unlike mosquitoes or horse flies, which possess specialized, rigid, piercing-sucking mouthparts, the adult brine fly is not a predator or a blood feeder. The adult stage is very short, often lasting only a few days, and their entire focus is on reproduction.
Some species of adult brine flies do not feed at all, relying entirely on energy stores accumulated as larvae. For those that do feed, their mouthparts are designed only for collecting microscopic particles, such as cyanobacteria and algae, from surfaces. Any sensation felt when near a swarm is not a bite, but rather the feeling of the harmless insects landing, crawling, or bumping into a person. These insects are not interested in humans as a food source.
Defining the Brine Fly: Habitat and Appearance
Brine flies are highly specialized insects that thrive in environments too harsh for most other life forms. They belong to the family Ephydridae, often called shore flies, and are uniquely adapted to hypersaline and alkaline water bodies. They are famously found in places like the Great Salt Lake in Utah and Mono Lake in California, where salt concentrations can be extremely high.
Adult brine flies are minute to small, typically ranging from 0.9 to 7.0 millimeters in length, and are generally black or gray. A remarkable adaptation allows the adult to walk underwater to lay eggs or forage on algae. They achieve this by trapping a thin layer of air, stabilized by dense, waxy hairs, which acts like a personal diving bell. The larval stage lives entirely submerged, feeding on detritus and algae at the lake bottom.
Why Brine Flies Are Important (And Sometimes Annoying)
Brine flies are a fundamental part of their unique ecosystems, despite often being perceived as a nuisance due to their overwhelming numbers. As larvae, they consume vast quantities of algae and organic matter, acting as primary decomposers in these salty environments. This cleaning function prevents the water bodies from becoming choked with microbial growth.
The sheer mass of brine flies represents a significant energy source for wildlife. These insects are a major food item for millions of migratory birds, including eared grebes, phalaropes, and gulls. A single brine fly can contain up to eight times the caloric value of a brine shrimp, making them a nutritious food source for birds refueling during migration.
The annoyance factor results purely from their immense population density and collective behavior. When billions of adult flies emerge, they form dark, moving bands along the shoreline, creating the appearance of a living carpet. Despite their swarming, the flies are not aggressive; they often part their crowds to avoid human footfalls and only fly up briefly if their resting area is disturbed.