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Sandy cased caddis (Pycnocentrella)

Taxonomic group

Helicophidae: Pycnocentrella

Diagnostic features

Pycnocentrella caddis larvae construct mobile cases covered in sand grains. They look much like the more common Pycnocentria, but Pycnocentrella have a distinctive comb-like row of hairs on the front/side edge of the pronotum (first segment behind the head).

Typical habitats

Pycnocentrella larvae are much less common than the similar-looking Pycnocentria, but they are most likely to be found in gravelly, bush covered streams.


They are collector-gatherers (feeding on fine particulate matter including algae) and shredders (feeding on leaf litter).

Indicator value

  • Hard bottom: 9
  • 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

The presence of Pycnocentrella larvae indicates good habitat and water quality, particularly if a range of mayfly and stonefly nymphs are also present. They have a high tolerance value of 9 for hard bottom sites (there is no soft bottom value).