“Net-spinning Caddisflies, Common Netspinners, Seine-net Weavers”
There are 47 genera in the family globally, with about 13 found in the US, including more than 155 species. Larvae build stationary retreats of silk, detritus and rock fragments. A part of the entrance of a retreat has a silken filter net protruding into the current to strain food from the water. This is how they earned the common name, “net spinners”. The mesh size of the filter net varies among hydropsychid species, corresponding with the current speed of their optimal habitat and the size of the food particles on which they specialize. They spend most of their life hiding in their retreats, waiting for food to get caught in their nets, mostly tiny bits of organic debris, but occasionally small animals; they sometimes also scrape algae from the surfaces of the rocks or other substrates to which their retreats are attached. Members of this family are often thought to be tolerant of pollution, but this is a misconception as tolerance varies greatly among the different species.
Order:Larvae: Wings/wing pads absent. Eye spots present, but compound eyes absent. Antennae usually small, inconspicuous. Three pairs of segmented legs present on thorax. Pair of anal prolegs, each with single hook, located on last abdominal segment. Larvae can be free-living, in silken retreats attached to substrate, or in usually-portable tubes or cases made of sand, rocks, or plant material.
Family:Pro-, meso-, and metanota entirely covered by sclerites. Ventral side of abdomen with rows of branched gills. Conspicuous tuft or fan of long hairs on each anal proleg. Anal claw with stout apical hook. Larvae building stationary retreats of silk, detritus, and rock fragments and add a silken net for filter feeding.
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