Spiral cased caddis (Rakiura)

Taxonomic group

Helicopsychidae: Rakiura

Diagnostic features

Rakiura caddis larvae construct a small mobile case made of sand grains arranged in a spiral. Unlike the related Helicopsyche, Rakiura has a chimney-like upward extension from the middle of the case.

[Rakiura]. Image: Stephen Moore Image — Rakiura. Image: Stephen Moore

Typical habitats

Rakiura larvae are common in some bush-covered streams in the South Island.

Feeding

They are likely to be “collector-gatherers” (as are Helicopsyche), feeding on a range of organic matter accumulating on stream beds.

Indicator value

Hard bottom: 10
Soft bottom: unassigned

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

Rakiura larvae are generally found in streams with good habitat and water quality, hence the maximum tolerance value of 10 for hard bottom sites (there is no soft bottom tolerance value).