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DIPTERA, Chironomidae -- <Images> & <Juveniles>

Description & Statistics

The true midges are primarily aquatic, although some develop in decaying vegetable matter or manure or in the soil. Aquatic species feed on algae, decaying vegetable matter, small crustaceans, etc. Members of the subfamily Tanypodinae subsist largely on the larvae of other Chironomidae. However, Trissocladius equitans Claas, seems to be a true external parasite of the nymphs of a mayfly, Rithrogena (Claassen 1922). Larvae of various instars except the first were found on the mesothorax under the wing pads, and the head was embedded in the tissues. A sheet of silk is spun over the body and is attached along its entire margin to the body f the host, so that no outside feeding can take place. The larva is thus closely confined to the body of the host. In younger developmental stages, the larva lies across the host's abdomen, but later it assumes a V-shaped position. Pupation occurs beneath the web, and the pupa works its way out from beneath this covering to ascent to the water surface just before emergence of the adult. Dactylocladius brevipalpus Galt was recorded as parasitic on mayfly nymphs of Rithogena sp. and other genera in France. The larvae were found only beneath the wing pads, and the species is believed to be a true parasite rather than a commensal (Dorier 1938, Clausen 1940).

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. This is a large group of insects with over 5010 described species and 705 species in North America alone. Males are easily recognized by their plumose antennae. Adults are sometimes known as "lake flies" in parts of Canada, as "sand flies", "muckleheads", or "muffleheads" in various regions of the USA Great Lakes area, and as "blind mosquitoes" or "chizzywinks" in Florida, North America. Their amazing biodiversity often goes unnoticed because Chironomidae are notoriously difficult to identify and are usually recorded by species groups by ecologists. Each morphologically distinct group consists of a number of morphologically (sibbling) 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 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

The larvae 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". Their ability to capture oxygen is further increased by making undulating movements.

Adults can be pestiferous 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.

Larvae and pupae are important as food items for fish such as trout and other aquatic organisms. The flying midges themselves are also eaten by fish, and insectivorous birds such as swallows and martins. The larvae are consumed by certain amphibians, such as the rough-skinned newt. They are also used by fly anglers, who design and tie imitators to catch trout.

They are also important as indicator organisms, i.e., the presence, absence, or quantities of various species in a given body of water can indicate whether pollutants may be present. Their fossils are also widely used by palaeolimnologists as indicators of past environmental changes, including past climatic changes.

References: Please refer to <biology.ref.htm>, [Additional references may be found at: MELVYL Library ]

Clausen, C. P. 1940. Entomophagous Insects. McGraw-Hill Book Co., NY. & London. 688 p.