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Guide to New Zealand's freshwater invertebrates
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 larvae are most abundant in stony, bush-covered streams.
They construct filter-feeding nets attached to the streambed to trap drifting particulate food items, including algae and other invertebrates.
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).