Montana Field Guide

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The early instars are free swimming (no case), small wormy-larvae with long ‘spidery’ legs. All instars of this family are relatively small, giving them the common name of ‘micro caddis’. Hydroptilid Cases are quite distinctive-- purse-shaped and transparent (or sand & algae covered), constructed from a glue-like secretion & silk from the mouth often incorporating sand grains or algal material.

Hydroptilid larvae occur in still and flowing freshwaters, generally on upper surfaces of rocks and boulders or amongst filamentous green algae or on macrophytes. Some species can be found in the splash zone of waterfalls or cascades, often aggregating in crevices amongst algal, liverwort and moss growths.

Most larvae are grazers or collector feeding on filamentous green, epilithic micro-algae, periphyton and filamentous diatoms. Orthotrichia larvae are often found in insect egg masses on the undersides of rocks and stones, apparently feeding on the eggs.

Most Hydroptilid Cases are purse-shaped and transparent, constructed from a glue-like secretion & silk from the mouth often incorporating sand grains or algal material. The hydroptilid life cycle differs from that of other Trichoptera in that larvae are only cased in the fifth (final) instar, but free-living for the first four instars, which are short in duration. Before pupation the larva attaches the case to the substratum. Some species aggregate on upper surface of rocks at pupation, others may pupate singly on or beneath rocks.

The hydroptilid life cycle is usually 1 year and mating takes place in the late spring and summer months when the adults hatch. Eggs are laid on the water surface or slightly underneath by the females and adhere to rocks or aqautic vegetation