Caddis fly

Insects in the Order Trichoptera. The order name means “hair wing” in Latin. There are 15 sub-orders with over 5,000 species, and 1,200 living in various aquatic habitats throughout North America. They are particularly abundant in most trout streams throughout the world. Caddis flies are some of the most important members of the macro invertebrate community that make up the food webs of most rivers and streams. They undergo complete metamorphosis (egg - larva - pupa - adult fly). Most are filter-feeders, while some are entomophagus (i.e., they eat other insects).

Links
  http://sites.state.pa.us/PA_Exec/Fish_Boat/sepoct99/cadisfly.htm