Chironomid midge (Orthoclad)

Taxonomic group

Chironomidae: Orthoclad

Diagnostic features

The Orthocladiinae is a large subfamily of the Chironomid midges. Like other chironomids the general body form is worm-like, but with a distinct head, and with paired prolegs under the head and at the end of the abdomen. Orthoclad larvae have a green or pale body, brown or pale head, with eyes consisting of one or two joined spots, the larger spot being behind and higher than the smaller one. The head has a thin black collar. Orthoclads are often found inside silt tubes.

[Orthoclad] midge emerging from silt tube. Image: Stephen Moore. Image — Orthoclad midge emerging from silt tube. Image: Stephen Moore.

[Orthoclad] midge heads. Image: Stephen Moore Image — Orthoclad midge heads. Image: Stephen Moore

Typical habitats

Orthoclad larvae are found in a wide range of stony, gravelly, algae-covered or weedy streams, particularly in farmland and urban areas.

Feeding

They are collector-gatherers feeding on streambed algae and other fine organic matter

Indicator value

Hard bottom: 2
Soft bottom: 3.2

The tolerance values (ranging from 0 to 10) give an indication of which are the sensitive taxa (values of 8 or more) and which are the tolerant taxa (values of 3 or less). For more information see: Indicator species

Orthoclads are often abundant in unshaded, nutrient-enriched streams with prolific algal growths. They have low tolerance values of 2 (hard bottom sites) and 3.2 (soft bottom sites).