936 FRESH-WATER BIOLOGY 



6 (5) Last abdominal segment bifurcated, the fleshy forks each bearing a 



pair of hooks and a minute, external, lateral filament; con- 

 spicuous lateral filaments on abdominal segments 1-8. . 7 



7 (8) Lateral filaments with no tuft of fine tracheal gills at their bases. 



Chauliodes. 



8 (7) Lateral filaments each with a tuft of fine tracheal gills at its base. 



Corydalis. 



KEY TO NORTH AMERICAN CADDISFLIES 



1 (2) Micro-caddisflies; very small, mothlike, hairy, the fore wings bearing 



numerous erect clavate hairs; the marginal fringe of the 

 wings longer than their greatest breadth; form of wings 

 narrowly lanceolate; antennae rather stout and not longer 

 than fore wings . Family HYDROPTILIDAE. 



2 (i) Larger caddisflies, with broader wings; marginal fringes never as long 



as the wings are broad; antennae usually longer than the fore 

 wings 3 



3 (26) Maxillary palpus five-jointed 4 



4 (19) Last joint of the maxillary palpus simple, and not longer than the 



other joints 5 



5 (10) Ocelli present 6 



6 (9) Front tibiae with two or three spurs, middle tibiae with four spurs . 7 



7 (8) The first two joints of the maxillary palpus short and thick, the third 



joint much longer and thinner. . Family RHYACOPHILIDAE. 



8 (7) The second joint of the maxillary palpus much longer than the first. 



Females. . Family PHRYGANEIDAE. 



9 (6) Front tibiae with a single spur, or with none; middle tibiae with only two 



or three spurs. Females. ... Family LIMNOPHILIDAE. 



10(5) Ocelli wanting n 



ii (12) A closed cell in the principal fork of the median vein in the fore wings. 



Family CALAMOCERATIDAE. 



12(11) No closed cell in the median fork 13 



13 (18) A closed cell in the first fork of the radial sector (R 8 ) 14 



14 (17) Both branches of the radial sector forked. . . ... . .. 15 



15 (16) Veins RI and R 2 confluent apically or connected by an apical cross 



vein in the fore wing. Females. . Family ODONTOCERIDAE. 



16 (15) Veins RI and R 2 not connected apically. 



Family SERICOSTOMATIDAE. 



17 (14) Only the anterior branch of the radial sector forked. 



Family LEPTOCERIDAE. 



18 (13) No closed cell in the first fork of the radial sector. 



Family MOLANNIDAE. 



19 (4) Last joint of the maxillary palpus usually much longer than the others, 



twisted, and divided imperfectly into subsegments. . . 20 



20 (21) Ocelli present Family PHILOPOTAMIDAE. 



