Free-living caddis (Plectrocnemia)

Taxonomic group

Polycentropodidae: Plectrocnemia

Diagnostic features

Plectrocnemia caddis larvae have no mobile case, no chelae (pincers) and they have a speckled head pattern. There is a curved line of small dark spots running across the middle of the head.

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

[Plectrocnemia]. Curved line of dark spots. Image: Stephen Moore Image — Plectrocnemia. Curved line of dark spots. Image: Stephen Moore

Typical habitats

Plectrocnemia larvae are occasionally found in gravelly streams with slow to moderate current speeds throughout New Zealand.

Feeding

They construct delicate filter-feeding nets to trap drifting particulate food items, possibly including other invertebrates and plant fragments.

Indicator value

Hard bottom: 8
Soft bottom: 6.6

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

Plectrocnemia larvae can be an indication of good water quality, particularly if they are found along with a range of mayfly and stonefly taxa. They have tolerance values of 8 (hard bottom sites) and 6.6 (soft bottom sites).