THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

Aquatic Invertebrates in Pacific Northwest Freshwater Wetlands
An Identification Guide and Educational Resource

Saddlecase makers are not common in wetlands, but can be so common and abundant in streams and rivers of the Northwest that the small cases of the early instars feel like a gritty coating on a rock's surface. They hang on to rocks with their anal prolegs and extend their head and front legs from the case to scrape algae off rocks, often pivoting on their anal prolegs.

The cases are oblong domes made from sand and rock fragments, sometimes using surprisingly large pieces. The bottom has an opening at each end with a flat plate of sand between the holes. Unlike other portable case makers, glossomatid cases can not be easily enlarged as the larvae grow. When they need a larger home, they build a new case off the end of the existing one and move in when they are done building, casting away the old case.

They often leave their unique cases when collected or stressed, but the body is easily identified. The larvae are more similar in appearance to the fixed shelter builders (Philopotamidae, Polycentropodidae, and Psychomyiidae) and the free living caddisflies (Rhyacophilidae) than to other case makers. The pronotum is always covered with a large plate, as is the top of the ninth abdominal segment. The tops of the other thoracic segments most often lack plates, but do have two or three small plates in some genera. Their anal prolegs are fairly well developed and visible, a trait more characteristic of shelter builders than case makers.