HYDROPTILID&. 
the edges of rocks in swift streams, or hang in masses in waving 
tufts of Cladophora. 
The cases of the described species are all portable, except those 
of Ithytrichia confusa, which is tightly cemented to rocks in mov- 
ing water. The cases vary greatly in form in different species. 
For the most part they are made of pure silk, but some have a 
sparse interweaving of sand grains or filaments of green alge. 
DescRIPTION OF THE Larva:.—The mandibles are asymmet- 
rical. The antenne are large, almost as long as the mandibles. 
Each thoracic segment bears a four-cornered shield. The pro- 
sternal horn is lacking. The middle of the abdomen is much larger 
than the thorax; spacing-humps are absent. The dorsal surface 
of the abdominal segments often bears chitinous plates. The pro- 
legs are short, with short, stout claws. 
The chitinous armature of the larve offers excellent char- 
acters for classification which, together with the interesting habits 
of the species, offers a promising field for future investigation. 
11g 
