What Bug Is That? The guide to Australian insect families.

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Chironomidae

Overview

The Chironomidae are a species-rich family with over 5,000 described species worldwide. The vernacular name for the family of 'non-biting midges' derives from the weak development of the adult mandibles, in contrast to the sister group, the biting midges (Ceratopogonidae), in which the female mouthparts are often designed for taking a blood meal. For certain larvae, the name of 'bloodworms' derives from the presence of the red blood pigment haemoglobin - but not all chironomid larvae are red. This family contains wingless genera.

Larval chironomid species track ecological conditions closely, and their distributions have long been used to assess water quality. This topic is well reviewed by Johnson (1995) in a volume that provides substantial reference to Australian studies of the ecology and systematics of the family (Cranston 1995). More general information on the family, its systematics, ecology and impacts upon humans is covered in Armitage et al. (1994).

Adult Chironomidae are most distinctive when the males form aerial swarms close to the natal site. Although adult chironomids are short-lived, their abundance in mass swarms close to eutrophic water bodies may cause nuisance, even inhalant allergies.

The ecology of the Chironomidae is very diverse and can scarcely be summarised except for the species-poor subfamilies. Thus larval Aphroteniinae are restricted to sandy substrates with fine organic material overlying. The Podonominae tend to cool stenothermy, are usually lotic, and are usually limited to winter periods. The Tanypodinae are predominantly predators in late instars, though often feeding on diatoms, etc, in early instars. The Telmatogetoninae are exclusively marine and inter-tidal, as are a few Chironominae. The Chironominae are all aquatic, and have an extraordinary range of biologies, though there is a preponderance of eurythermic taxa compared to the other subfamilies. The Orthocladiinae tend more to cool stenothermy, but are very diverse and include riparian, terrestrial and phytotelm species.

Description

In the male, the plumose antenna with elongate apical flagellomere is characteristic, and in both sexes the single branch of the wing vein M is diagnostically different from the 2-branched condition in Ceratopogonidae. Three branches of R may reach the margin - R2+3 ranges from strong to attenuate, sometimes running so close to R1 that it is indistinct. The female mouthparts lack toothed mandibles, except in Austrochlus Cranston.

Chironomid larvae are apneustic, with one exception, the amphipneustic genus Austrochlus whose larvae develop in pools on isolated granite outcrops in Western Australia and a few central Australian sites. The prolegs are nearly always present, and paired on the prothorax and final abdominal segment. The head capsule is always prognathous (directed forwards) thus differentiating from Thaumaleidae. For 95% of aquatic species, separation from the Ceratopogonidae, can be made using the prolegs, which are paired and separate. A few Orthocladiinae confuse the situation, and it may be necessary to examine the pharyngeal apparatus which is strong, with divergent arms in ceratopogonid larvae, but weak in Chironomidae.

Distribution

Chironomidae are cosmopolitan and distributed globally, even to Antarctica, where they include the southernmost holometabolous insects. Endemism at generic level in Australia is quite low since many genera are distributed on the other southern continents (a 'Gondwanan' distribution). Northern elements are shared with South-east Asia.

  • Chironomidae

  • Chiromonidae

  • Chironomidae

  • Chironomidae

  • Chironomus sp.

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