| Chironomidae | |
|---|---|
| Male Chironomus plumosus | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Diptera |
| Suborder: | Nematocera |
| Infraorder: | Culicomorpha |
| Superfamily: | Chironomoidea |
| Family: | Chironomidae |
| Genera | |
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Chironomidae (informally known as chironomids or non-biting midges) are a family 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 elongate mouthparts of the Culicidae.
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This is a large taxon of insects; some estimates of the species numbers suggest well over 10000 world-wide.[1] Males are easily recognized by their plumose antennae. Adults are known by a variety of vague and inconsistent common names, largely by confusion with other insects. For example chironomids are known as "lake flies" in parts of Canada, as "sand flies", "muckleheads",[2] or "muffleheads"[3] in various regions of the USA Great Lakes area, and as "blind mosquitoes" or "chizzywinks" in Florida, USA.[4] However, they are not mosquitoes of any sort, and the term sandflies generally refers to biting flies unrelated to the Chironomidae.
The biodiversity of Chironomidae often goes unnoticed because they are notoriously difficult to identify and ecologists usually record Chironomidae by species groups. Each morphologically distinct group comprises a number of morphologically (sibling) identical species that can only be identified by rearing adult males or by cytogenetic analysis of the polytene chromosomes. Polytene chromosomes were originally observed in the larval salivary glands of Chironomus midges by Balbiani in 1881. They form through repeated rounds of DNA replication without cell division, resulting in characteristic light and dark banding patterns which can be used to identify inversions and deletions which allow species identification.
Larval stages of Chironomidae can be found in almost any aquatic or semiaquatic habitat, including treeholes, bromeliads, rotting vegetation, soil, and in sewage and artificial containers. They form an important fraction of the macro zoobenthos of most freshwater ecosystems. They are often associated with degraded or low biodiversity ecosystems because some species have adapted to virtually anoxic conditions and are dominant in polluted waters. Larvae of some species are bright red in color due to a hemoglobin analog; these are often known as "bloodworms".[5] Their ability to capture oxygen is further increased by making undulating movements.[6]
Many reference sources in the past century or so have repeated the assertion that Chironomidae do not feed as adults, but an increasing body of evidence contradicts this view. It now is widely accepted that adults of many species do in fact feed. The natural foods reported include fresh fly dropping, nectar, pollen and honeydew and various sugar-rich materials. [1]
The question whether feeding is of practical importance has by now been clearly settled for some Chironomus species at least; specimens that had fed on sucrose flew for far longer than starved specimens, and starved females longer than starved males, which suggested that they had eclosed with larger reserves of energy than the males. Some authors suggest that the females and males apply the resources obtained in feeding differently. Males expend the extra energy on flight, while females use their food resources to achieve a longer life-span. The respective strategies should be compatible with maximal probability of successful mating and reproduction in those species that do not mate immediately after eclosion, and in particular in species that have more than one egg mass maturing, the less developed masses being oviposited after a delay. Such variables also would be relevant to species that exploit wind for dispersal, laying eggs at intervals. Chironomids that feed on nectar or pollen may well be of importance as pollinators, but currently evidence on such points is largely anecdotal. However, the content of protein and other nutrients in pollen, in comparison to nectar, might well contribute to the females' reproductive capacity. [1]
Adults can be pests when they emerge in large numbers. They can damage paint, brick, and other surfaces with their droppings. When large numbers of adults die they can build up into malodorous piles. They can provoke allergic reactions in sensitive individuals.[7]
Larvae and pupae are important food items for fish such as trout and sticklebacks and for other aquatic organisms. An amphibian that eats them is the rough-skinned newt.[8] Many aquatic insects such as various predatory Hemiptera in the families Nepidae, Notonectidae and Corixidae eat Chironomidae in their aquatic phases. So do predatory water beetles in families such Dytiscidae and Hydrophilidae. Fly anglers design and tie imitators to catch trout. The flying midges are eaten by fish and by insectivorous birds such as swallows and martins. They also are preyed on by bats and flying predatory insects such as Odonata and dance flies.
Chironomidae are important as indicator organisms, i.e., the presence, absence, or quantities of various species in a body of water can indicate whether pollutants are present. Also, their fossils are widely used by palaeolimnologists as indicators of past environmental changes, including past climatic variability.[9]
The family is divided into eleven subfamilies: Aphroteniinae, Buchonomyiinae, Chilenomyinae, Chironominae, Diamesinae, Orthocladiinae, Podonominae, Prodiamesinae, Tanypodinae, Telmatogetoninae, Usambaromyiinae.[10][11]
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