Chironomidae

Chironomids together with other insects are defined as 'temporary meiofauna' because the small larval stages (instars) fall within the size category of meiofauna. Their larvae and pupae are found in all aquatic and moist, terrestrial habitats. Chironomids are the most abundant and species-richest group of aquatic insects with larval body lengths between 0.2 and 30 mm)1. In many freshwater systems, such as in streams and rivers, often more than 100 different chironomid species do substantially contribute, together with other meiobenthic species, to the biodiversity of streambed communities.

• Larval densities can reach more than 0.5x106 individuals/m2, with higher abundances often deep in the streambed sediment 2,3. Distinct seasonal shifts in the spatial distribution of the larvae, may often reflect the shifts in the availability of food sources3,4.
• Many chironomid species display high biomass turnover and production rates. Larvae feed on bacteria, algae, other uni- and multicellular invertebrates and particulate organic matter4 while other freshwater invertebrates, fish and birds prey upon chironomids. Consequently, larval chironomid species contribute substantially to freshwater food-web dynamics5-8.
• Larval chironomids have cylindrical bodies with a distinct head and a pair of prolegs on the prothorax and another pair on the caudal segment. They occur in a wide variety of colours ranging from yellow, green, blue to purple. Much of larval species identification relies on mouthpart morphology and body setation1.
• Identification of larval species is often assisted through reared material and certain genera are also cytogentically assessed. Adult chironomids are tiny, delicate, long-legged, non-biting midges (mostly ≤ 5 mm), frequently emerging simultaneously in large numbers from lakes and rivers.