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Spiral cased caddis (Helicopsyche)

Taxonomic group

Helicopsychidae: Helicopsyche

Diagnostic features

Helicopsyche caddis larvae construct a small mobile case made of sand grains arranged in a spiral. At first glance they might be mistaken for small snails, but the legs of the caddis larva can be seen when the larva moves.

Typical habitats

Helicopsyche larvae are common in many stony or gravelly, bush-covered streams.


They are “collector-gatherers”, feeding on a range of organic matter accumulating on stream beds.

Indicator value

  • Hard bottom: 10
  • Soft bottom: 6.8

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 Helicopsyche larvae indicates good habitat and water quality conditions, especially if mayfly or stonefly groups are also abundant. They have high tolerance values of 10 (hard bottom sites) and 8.6 (soft bottom sites).