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Free-living caddis (Hydrobiosis)

Taxonomic group

Hydrobiosidae: Hydrobiosis

Diagnostic features

The New Zealand hydrobiosid caddis larvae have pincers on their forelegs. Several of the common hydrobiosid species belong to the genus Hydrobiosis. Depending on the species, the prosternal plate (shield-like structure between the forelegs) may be a single, roughly square plate (e.g. H. parumbripennis and H. centralis), or divided into 3 pieces (e.g. H. clavigera and H. silvicola).

Typical habitats

Hydrobiosis larvae are common in stony streams all over New Zealand, in bush-covered and farmland areas.


They are predators, feeding on other stream invertebrates.

Indicator value

  • Hard bottom: 5
  • Soft bottom: 6.7

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

Hydrobiosis larvae can be common in streams with moderate to good water quality. They have mid-range tolerance values of 5 (hard bottom sites) and 6.7 (soft bottom sites).