Zelolessica caddis larvae construct mobile cases of sand grains, sometimes mixed with plant fragments. The tail end of the case is angled, and has an opening wider than long. There is a fringe of long black hairs on the front edge of the pronotum (first segment behind the head).
Zelolessica larvae are commonly found in bush covered, stony streams, often amongst aquatic mosses.
They are collector-gatherers, known to feed on organic detritus and streambed algae.
An abundance of Zelolessica larvae is an indication of good water quality, particularly where mayfly and stonefly nymphs are also abundant. They have tolerance values of 10 (hard bottom sites) and 6.5 (soft bottom sites).