Nerve- winged Insects; Scorpion-flies; Caddis-flies 245 



Head elliptical, only pronotum (dorsal wall of prothorax) chitinized (homy 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. 

 .■\bdomen much thicker than the thora.x; 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. 



HVDROPSYCHID.E. 



