British Species of Caddis-fties. 123 
teriorly ; in some the head and three thoracic segments are all 
corneous, in others the metanotum is not corneous; mandibles 
strongly dentate; legs short; terminal abdominal segment with 
long anal crotchets ; respiratory filaments arranged in tufts, or not 
visible externally. 
Pupa rather stout, lying free within the case ; mandibles inter- 
nally dentate; abdomen not fringed, sometimes with external 
respiratory filaments. 
Case a fixed heap of small stones, or sometimes a channel is 
formed of sand on the surface of a large stone. The larve some- 
times live free beneath stones and only form cases when about to 
metamorphose. 
Most of the genera inhabit running waters, but some frequent 
ponds and canals. 
As the genera in this family are in most instances founded on 
characters afforded by the neuration, especially of the apical por- 
tion of the wing, the following scheme for numbering the apical 
forks (suggested by Dr. Hagen) will be found very serviceable, 
and I only regret that I could not see my way clear to the 
intelligible adoption of it in the other families. 
Taking the genus Hydropsyche as the most complete example, 
we find in the anterior wings that the two branches of the ramus 
discoidalis fork at the ends, forming a cell ; these we call forks 
Nos. 1 and 2. Again, both the branches of the upper or an- 
terior branch of the ramus thyrifer fork at their extremities ; 
these furcations we call forks Nos. 3 and 4. Finally, the lower 
branch of the ramus thyrifer (the ramus clavalis of Kolenati) 
forks at the end, and forms fork No. 5. 
In the posterior wings a similar arrangement may be seen. 
Thus the two branches of the ramus discoidalis fork and form 
Nos. 1 and 2; the upper branch of the anterior branch of the 
ramus subdiscoidalis forks and forms No. 3; and the lower branch 
of the ramus subdiscoidalis forks and forms No. 5; fork No. 4 
is never present in these wings. 
A reference to the Garnes of the neuration of these genera 
(Plates VII., VIII.), in iaihiigh all the forks are ehaabicuieds will 
render this arrangement easily understood. 
The genera may be arranged according to the presence of the 
forks in the anterior wings, thus :— 
Forks 1, 2, 3,4, 5 . « Hydropsyche, Diplectrona, Philo- 
potamus, Plectrocnemia, Polycen- 
tropus, Ecnomus,aud Neureclipsis. 
Forks 1, 2,3,5 . : « Wormeldia. 
Forks 2,3,4,5 . . . Vinodes, Psychomia, and Cyrnus. 
