Chironomid midge (Chironomus)

Taxonomic group

Chironomidae: Chironomus

Diagnostic features

Chironomus is one of our best known midges, with larvae commonly referred to as “blood worms” due to their vivid red colour (when live). 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. In Chironomus the eyes are split into two well-separated parts, one above the other, and tubular “blood gills” are visible near the end of the abdomen.

[Chironomus]. Ventral “blood gills”. Image: Stephen Moore Image — Chironomus. Ventral “blood gills”. Image: Stephen Moore

[Chironomus]. Widely separated double eyes. Image: Stephen Moore Image — Chironomus. Widely separated double eyes. Image: Stephen Moore

Typical habitats

Chironomus larvae are common in the soft sediments of slow-flowing streams, lakes or ponds, even in sewage ponds.

Feeding

They feed on a wide range fine organic matter settling to the sediments of pool habitats.

Indicator value

Hard bottom: 1
Soft bottom: 3.5

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

An abundance of blood-red Chironomus indicates low oxygen in the sediment, often the result of organic nutrient enrichment. They have low tolerance values of 1 (hard bottom sites) and 3.5 (soft bottom sites).