RHYACOPHILID&. 
dropped into strong alcohol the cocoon collapses, giving additional 
evidence that it contains no openings. 
Foop.—The Rhyacophiline sometimes eat filamentous alge, 
but show a preference for small larve. The larve are taken into 
the stomach entire, without any chewing or mutilation. 
The food of the Glossosomatine is not known. Stomachs ex- 
amined contained a structureless material that could not be identi- 
fied. 
EMERGENCE.—Some species emerge throughout the entire 
summer, while the transformation of others is restricted to a short 
period. 
Description oF Larva‘.—The abdomen consists of nine seg- 
ments; the prolegs are not fused to form an apparent tenth seg- 
ment. Spacing-humps, prosternal horn, and lateral fringe are ab- 
sent ; external gills are absent on all known American species, but 
occur on some European species; rectal gills are present on some, 
perhaps all, species, but are usually retracted and not easily seen; 
the abdomen is but little wider than the thorax. 
Key To THE LARVA: OF RHYACOPHILIDA. 
A. Drag-hooks plainly more than half as long as last abdominal 
segment. Without transportable cases—kKhyacophiline. 
A.A. Drag-hooks plainly less than half as long as last abdominal 
segment. Larve with transportable cases—Glossosoma- 
tine. 
SUB-FAMILY RHYACOPHILIN#. 
Description oF Larvas.—The head is long and flattened, 
truncate at the cephalic margin. The abdomen is depressed, with 
deep constrictions at the sutures; the prolegs are well developed, 
and extend parallel to the axis of the body; their claws are long. 
The maxillary lobes are long and slender. 
RHYACOPHILIN-E. 
A. Apparently two pairs of well-developed drag-hooks. Con- 
spicuous dark-brown pattern passes transversely across 
middle of head—Rhyacophila fuscula. 
A.A. Apparently but a single pair of well-developed drag-hooks. 
No transverse pattern across middle of head.—Rhyacophila 
torva. 
III 
