Polyplectropus caddis larvae have no mobile case, no chelae (pincers) and they have a distinctly speckled head pattern. The head pattern does not include a curved line of spots (the related Plectrocnemia has a curved line of spots across the head).
Polyplectropus larvae are common in slow-flowing gravelly streams, or soft bottom streams with woody debris, throughout New Zealand.
They construct delicate filter-feeding nets to trap drifting particulate food items, possibly including other invertebrates and plant fragments.
Polyplectropus larvae are most common in streams of moderate to good quality, as reflected by their tolerance values of 8 (hard bottom sites) and 8.1 (soft bottom sites).