Net-building caddis (Orthopsyche)

Taxonomic group

Hydropsychidae: Orthopsyche

Diagnostic features

Hydropsychid caddis larvae have hardened (sclerotised) plates on each of the 3 thoracic segments, and gill tufts under the abdomen. Orthopsyche larvae have 6 sets of abdominal gills (7 in the related Aoteapsyche and Diplectrona). The Orthopsyche abdomen is also covered by coarse stubble (fine hairs in the other 2 genera). There are 4 anal gills at the end of the abdomen (5 anal gills in Diplectrona).

[Orthopsyche]. Image: Stephen Moore Image — Orthopsyche. Image: Stephen Moore

[Orthopsyche]. 4 anal gills. Image: Stephen Moore Image — Orthopsyche. 4 anal gills. Image: Stephen Moore

Typical habitats

Orthopsyche larvae are most abundant in stony, bush-covered streams.

Feeding

They construct filter-feeding nets attached to the streambed to trap drifting particulate food items, including algae and other invertebrates.

Indicator value

Hard bottom: 9
Soft bottom: 7.5

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 Orthopsyche larvae, particularly in combination with mayflies and stoneflies, is an indication of good water quality. They have high tolerance values of 9 (hard bottom sites) and 7.5 (soft bottom sites).