Key to Families of Australian Trichoptera Larvae

Trichoptera (Caddisflies) are small, moth-like insects with winged adults and aquatic larvae. The larvae differ from those of Lepidoptera (moths and butterflies) in having only one pair of abdominal prolegs (on segment 10) rather than five (on 3, 4, 5, 6 and 10)

Many trichopteran larvae build moveable cases out of sticks, leaves, reed stems or sand grains, while the free-living species generally construct silken nets or retreats underwater. The cases alone often are sufficient to identify specimens to the family level. Cases often, however, become damaged or are abandoned on handling and many specimens obtained from bulk collecting methods cannot be directly associated with their case. Examination of the animal, or at least the head, is frequently necessary for family level identification, and a full examination generally is necessary for identification to genus and species.

This Key to Trichopteran larvae includes characters relating to case construction but mainly addresses the anatomy of the animal itself, which requires careful withdrawal of the animal from the case. The key covers 24 of the 25 families which occur in Australia. The larvae of Stenopsychidae is unknown but might resemble Polycentropodidae, to which family the adults of Australian species were previously referred. The key also covers the single family of Lepidoptera: Pyralidae, in which the larvae of some species are aquatic.

Note that this key works well for late instars, but should be used with caution for early instars (for example, gills may not be developed in some very young individuals). A particular problem applies to the Hydroptilidae (micro-caddis), which are keyed largely on the basis of an expanded abdomen. This is characteristic of final instar larvae only. Early instar Hydroptilidae are minute, free-living and rarely collected. They are not considered specifically in the key, but can often be recognised by their tiny size, lack of a case and slender, somewhat spidery/sprawled appearance. Many also have long setae trailing from the end of the abdomen (see second illustration in the Hydroptilidae taxon notes). Wells (1985) described early instars for some genera.

Key Author(s): CSIRO Entomology Key Version: 1.1