Nerve-winged Insects; Scorpion-flies; Caddis-flies 245 
Head elliptical, only pronotum (dorsal wall of prothorax) chitinized (horny and 
dark), abdominal constrictions deep; cases of vegetable matter laid longitudi¬ 
nally and forming a spiral, widening at front end. Phryganeid^e. 
Head oval to circular, pronotum chitinized, mesonotum often, and metanotum some¬ 
times chitinized, abdominal constrictions slight. 
Lateral fringe well developed; cases various... Limnophilid^e. 
Lateral fringe slightly developed; cylindrical case of sand or small stones. 
Sericostomatid.e. 
Larva with head projecting straight forward in line with the rest of body; tubercles 
and lateral fringe wanting; gill-filaments, when present, branched. 
Abdomen much thicker than the thorax; case kidney-shaped, of small stones, or flat 
and parchment-like. Hydroptilid^e. 
Abdomen little if any thicker than the thorax. 
Third pair of legs a little longer than the first pair; no larval case. .Rhyacophilid^e. 
Third pair of legs about the same length as first pair; no portable larval case. 
Hydropsychid^e. 
