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Sandy cased caddis (Pycnocentria)

Taxonomic group

Conoesucidae: Pycnocentria

Diagnostic features

Pycnocentria caddis larvae construct mobile cases covered (usually) in fine sand grains. Their orange-brown heads are rounded on top (not flat like in Pycnocentrodes). Some species arrange the sand grains in tight spirals (although some have gaps between the rings) but others nave no visible pattern in the sand grains.

Typical habitats

Pycnocentria larvae are common in streams with stony, gravelly or sandy beds, both in bush covered and farmland areas.


They are collector-gatherers known to feed on a range of algae found in stream bed biofilms.

Indicator value

  • Hard bottom: 7
  • 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 Pycnocentria larvae indicates at least moderate to good water quality (good water quality would be indicated by a wide range of mayfly, stonefly and caddisfly taxa). They have tolerance values of 7 (hard bottom sites) and 6.8 (soft bottom sites).