Skip to content

Taxonomic group

Hydroptilidae: Paroxyethira

Diagnostic features

Paroxyethira caddis larvae construct small, transparent, mobile cases shaped like a purse (hence the common name “purse caddis”). Each of the three thoracic segments has a hard (“sclerotised”) covering.

Typical habitats

Paroxyethira larvae are common in slow flowing, unshaded streams, particularly amongst weed beds or algal growths.


They feed on filamentous algae.

Indicator value

  • Hard bottom: 2
  • Soft bottom: 3.7

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

Abundances of Paroxyethira larvae are usually recorded at sites with abundant streambed algae or weed beds. Such growths are likely to be the result of nutrient enrichment, limited shade and a lack of recent high flow (algae scouring) events. They have low tolerance values of 2 (hard bottom sites) and 3.7 (soft bottom sites).