Common Name: Midges
Scientific Name: Various
Class / Order / Family: Insecta/Diptera/Chironomidae
The common name of midge means very or extremely small; in general, small species are sometimes referred to as small or young mosquitoes. Midges are primarily a nuisance pest and are commonly mistaken for mosquitoes. They can cause allergic reactions in susceptible individuals. There are about 817 species in the United States and Canada.
Adults about 1/32-3/8 (1-10 mm) long; slender body and wings, mosquito like. Color various, ranging from black to yellow, green, or pink/red. Head with mouthparts forming a short proboscis (beak), not adapted for piercing; ocelli absent. Male antenna usually plumose (feathery). Wings long and narrow, with thickened part of costa (C, front vein) ending near wing tip, media (M) unbranched, veins lacking scales. Front tarsi usually lengthened; when at rest, front legs usually raised and constantly vibrated. Mature larvae vary from 1/32-1 1/8″ (1-30 mm) long; elongate, cylindrical, usually slender with sclerotized (hardened) nonretractile head; color whitish, yellowish, greenish, purplish, pinkish, very deep red, or brownish; body 12-segmented, 1st thoracic segment with 2 prolegs and last abdominal segment usually with 2 prolegs.
(1) Mosquitoes (Culicidae) have wings with scales along veins and wing margin, and mouthparts elongated, adapted for piercing in females of most species.
(2) Dixid midges (dixidae) have distal/outer portion of wing with an unforked vein between 2 forked veins.
(3) Crane flies (Tipulidae) with very long legs, wing with media (M) branched/forked and 2 anal veins reach wing margin.
This can be summarized for two species widely distributed in the United States. 1. Chironomus attenuatus Walker. Mating takes place in the adult swarm. The female deposits a brown egg mass averaging 700 eggs on her hind femora for 2-3 minutes, and then drops the mass on a wet surface where it swells and sinks. There are 4 larval instars which feed on aquatic vegetation and organic matter, spending much of their time in mud tubes/burrows. After pupation is completed, the pupa leaves the larval burrow, swims to the surface, and the adult emerges within 4-5 seconds.
Adults probably live about 6 days. 2. Chironomus plumosus Linnaeus. Adults occur in swarms. The females deposit their egg mass of up to 2,000 eggs on the water surface of a large body of water, where the mass swells and sinks; 90+% of oviposition occurs within 1-2 hours after sundown. Eggs hatch in 3 days at 75F/24C to 14 days at 48F/9C. There are 4 larval instars with 2-4 living in U-shaping mud tubes, feeding on decayed algae and diatoms.
After pupation is completed in the larval tube, the pupa swims to the surface and the adult emerges in 15-30 seconds. Females die after depositing their egg mass. Most of the developmental time (egg to adult) is spent in the larval stage which can last from about 70 days to 3 years. The adults live at most several weeks.
The immature stages occur in nearly every habitat that is aquatic or wet, including ocean shore areas. Many species inhabit the soil and other terrestrial habitats rich in organic matter such as decayed vegetation, dung, fungi, mosses, and under bark. Most larvae live in fresh water and are found in fast moving mountain streams, lakes, drainage ditches, flood channels, ponds, reservoirs, tanks, and sewage treatment plants. Most are bottom feeders. They have a closed respiratory system and absorb dissolved oxygen directly from the water, so they do not have to surface for air.
Adults of each species typically emerge over a few days and form swarms of thousands of midges which can be a serious problem in lakefront communities. Swarming typically occurs around sunset and is usually composed of only males with females being attracted to the swarm. If attracted to structures by lights, females often deposit their gooey egg masses in the vertical surfaces of structures; the masses either dry hard or if wetted, leave an unsightly brown stain.
These massive swarms cause problems by their sheer numbers, not only covering the sides of buildings around lights but also getting in people’s eyes, mouth, and ears, and are sometimes inhaled. They can cause major problems at manufacturing plants where paper, plastics, and food products are made, and also at auto refinishing shops where they are typically attracted by the lights. They can travel at least about 1/4 mile (400 m) form their breeding source; often this is downwind from the breeding source.
The senior author has encountered midge problems at mini-market shops, a donut shop and a paper manufacturing plant. In each case, the problem occurred because of the use of large numbers of mercury-vapor lights on the building’s exterior and nearby water sources.
Follow the basic 5 steps of identification, inspection, sanitation, mechanical control/exclusion, and insecticide application if required. The key is to first make the structure less attractive and then to use exclusion. This is done with a night-time inspection to evaluate the exterior lighting and entry pathways.
All mercury-vapor lamps should be changed to sodium-vapor and change on-building lights to off-buildings lights. Around entrance/exit doors change white incandescent/flourescent bulbs to yellow bulbs but change only half the bulbs at any location at one time to let the people adjust, and after a couple of weeks, change the remainder unless security is a concern. Apply this same principle to lights on the interior of entrance/exit doors used by smokers exiting for their smoke breaks (check for accumulations of cigarette butts). Electrocutor-type insect light traps (ILTs) are effective if properly placed but be sure they cannot be seen from the outside.
Also at night, check to see which windows and doors are kept open for ventilation. These must be screened and the screen in good repair or if this is impractical, air curtains/doors which are wired to come on automatically when the door is open should be considered. The use of exterior decoy mercury-vapor lamps located at least 50 ft (15.2m) away from the structure.
Of the midges are coming from a nearby lagoon, pond, or small like, setting up these decoy lights so theat they hang about 4-6 ft (1.2-1.8 m) above and over the water can reduce the number of midges because many hit the water and drown and/or are eaten by fish or aquatic insects. In small bodies of water, control of midges has been achieved by stocking them with goldfish and carp at the rate of 150-500 lbs per acre (68-225 kg per 0.4 ha) of water surface. The indoor use of space treatments or ULV applications of non-residual insecticides will kill the midges present but more will come in the next night unless the lighting and entrance/exit door problems have been corrected.