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Brief Summary

    Chironomidae: Brief Summary
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    "Lake fly" redirects here. For species in the genus Chaoborus (family Chaoboridae), see glassworm.

     src= Two lake flies observed in Neenah, Wisconsin after the yearly hatch in Lake Winnebago.

    The Chironomidae (informally known as chironomids, nonbiting midges, or lake flies) comprise a families of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae. Many species superficially resemble mosquitoes, but they lack the wing scales and elongated mouthparts of the Culicidae.

    The name Chironomidae stems from the Ancient Greek word kheironómos, "a pantomimist").

Comprehensive Description

Distribution

    Distribution
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    Species of chironomid midges are found in moist or wet habitats in all major landmasses of the world, including Antarctica, and most islands.

    Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Native ); antarctica (Native ); oceanic islands (Native )

    Other Geographic Terms: cosmopolitan

Morphology

    Morphology
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    Adults are small (1-20 mm long, most less than 10 mm), slim, long-legged flies. They resemble, and are often confused with, mosquitoes (Culicidae), but unlike mosquitoes, they do not bite, and have no scales on their wings. Many species rest on their hind two pairs of legs, and hold their forelegs out in front of them. In most species, adult males have plumose antennae that are much larger than the females (these are probably used to locate females). Most species are dark-colored, usually brown or black.

    Larvae are elongate and cylindrical, with distinct segmentation and a hard sclerotized head capsule that cannot be retracted into the body. They have no true legs, but do have a pair of unjointed "prolegs" on the first segment of the thorax. The presences of this pair of prolegs, the absence of true legs, and the structure of the head are good distinguishing marks for identifying larvae in the Chironomidae. Color varies widely among larvae, most are tan or brown, but some are whitish, some are green. Larvae of a number of species in the subfamily Chironominae have the hemoglobin in their circulatory fluid, which helps them survive in low-oxygen habitats. These larvae are pinkish or red when alive, and are often called "blood midges."

    Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

    Sexual Dimorphism: sexes shaped differently

Habitat

    Habitat
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    Midge larvae occur in all kinds of benthic freshwater habitats, including the bottoms of streams, rivers, lakes, ponds, and temporary pools, also wetlands such as marshes and swamps. Some breed in isolated damp habitats such as tree-holes, pitcher plants, patches of moist soil, even dung pats. The "blood midges" or "bloodworms" are species of midges with hemoglobin in their hemolymph, which allows them to survive in low-oxygen (and often heavily-polluted) habitats. Adults rarely disperse far from the larval habitat.

    Habitat Regions: temperate ; tropical ; polar ; terrestrial ; freshwater

    Terrestrial Biomes: forest ; rainforest

    Aquatic Biomes: benthic ; lakes and ponds; rivers and streams; temporary pools; brackish water

    Wetlands: marsh ; swamp ; bog

    Other Habitat Features: riparian ; estuarine ; intertidal or littoral

Trophic Strategy

    Trophic Strategy
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    The many thousands of chironomid species have many different feeding habits. Most species feed on small particles of organic debris, but the size of particles varies, some shred bits of dead wood and leaves, some gather smaller particles, some even filter tiny particles suspended in the water. Some of these detritivores also collect algae cells, and some species are herbivores, specialize in feeding on algae. Other herbivores are "miners" tunneling in larger vascular plants. There are some fungivore chironomids as well, eating spores and grazing on hyphae. A few species are simple predators, often attacking other chironomid species.

    Primary Diet: detritivore

Associations

    Associations
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    Chironomids are the most diverse and abundant macroinvertebrates in most of the aquatic ecosystems they inhabit (and they inhabit most aquatic ecosystems). Most natural ponds, lakes and streams are home to 50-100 different species of non-biting midges. Collectively, they play a vital role in freshwater ecosystems as primary consumers. They harvest an enormous amount of energy from detritus and are one of the major supports for animal communities in these systems.

    Associations
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    Non-biting midges are so abundant in so many freshwater habitats that practically every kind of predator in these habitats feeds on them at some stage of their life cycle. Midges try to avoid predation by limiting their activity during daylight, and larvae and pupae take refuge in tunnels that they build in sediment. Many species are cryptically colored.

    Anti-predator Adaptations: cryptic

Life Cycle

    Life Cycle
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    Like all flies, the Chironomidae are holometabolous, and undergo metamorphosis in their life cycle. Adult females lay eggs in aquatic habitats. The larvae that hatch from these are often planktonic in their first instar, floating in the water column and feeding on microscopic particles in the water. After their first molt, larvae of most species descend to the bottom and remain benthic through the rest of the larval stage (usually four instars). The larvae transforms into a pupa, which often stays within a shelter or cocoon while it transforms into an adult. When it's time to emerge, the pupa swims to the surface, and the adult pulls itself out of its old skin.

    Development - Life Cycle: metamorphosis

Life Expectancy

    Life Expectancy
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    Lifespan varies greatly between and within species in the Chironomidae. Individual growth and development rates are strongly influenced by temperature and other environmental factors. Many temperate species live for a year, surviving the winter as larvae. Some species are known to complete entire life-cycles in a few weeks, if temperatures are warm and food is abundant.

Reproduction

    Reproduction
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    Adult non-biting midges often form mating swarms, either in the air near oviposition sites, or "skating" on the surface of water. These swarms are composed mostly of males, and may serve to attract females.

    In most species, eggs are laid in gelatinous masses on the water surface or on emergent vegetation. In some species, females lay their eggs in or under the water. Adult chironomids usually only live for a few days or weeks, and so reproduction is a single concerted effort. Most species breed seasonally. A very few species are reported to be parthenogenic, most have male and female adults

    Key Reproductive Features: semelparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); parthenogenic ; sexual ; fertilization (Internal ); oviparous

    No male investment. Female investment is in provisioning eggs and producing a protective gel mass for them.

    Parental Investment: pre-fertilization (Provisioning)