NORTH AMERICAN CADDIS-FLY LARVE. 
tube thus formed is lined from end to end with a tough cylinder 
of silk. Clumsy and bulky as the larval cases are, they do not 
vary greatly from cylindric form, nor do they have projecting 
twigs or corners that would catch during locomotion, nor chunks 
or stones that would be too heavy for the powerful larve to drag. 
In the pupal cases heavy stones and great fragments of bark are 
used, whose weight and form would make locomotion almost im- 
possible. 
PYCNOPSYCHE SCABRIPENNIS. 
HasitaT.—Specimens of this species were collected only in 
Spherium and Argus Brooks; but the larva and cases are so sim- 
ilar to Halesus, and probably to other genera, that it is by no 
means probable that its distribution is as restricted as our data 
would indicate. 
Hasits.—In the streams mentioned the larve are exceedingly 
abundant, crawling slowly over the bottom, or clinging with their 
heads pointing upstream, to submerged sticks and logs. In the 
latter position they sometimes completely cover sticks which are 
slightly above the stream’s bottom, but upon the slightest jar they 
relinquish their holds and float down with the current. 
Before pupation the larve leave the open water and hunt the 
seclusion of crevices in bark or root mats. At this time casual 
examination of the stream reveals not one larva in localities in 
which thousands previously formed the most conspicuous life on 
the bottom. 
Foop or Larva:.—Stomachs examined contained only raspings 
of decomposed wood, much of which was ground to fine powder. 
Prriop oF EmMERcING.—Adults appear during the last days of 
August and the first part of September. 
DescripTION oF Larva:.—Length, 25 mm.; breadth, 3.5 mm. 
Head.—The head, figure 88, is large; in dorsal view it has 
almost parallel sides, slightly curved caudal margin and almost 
straight cephalic margin; in color it is straw-yellow, with a vary- 
ing pattern of round or oval muscle-attachment marks, and shad- 
ings of dark-brown; on the ventral surface the brown muscle- 
attachment marks are confined to the caudal half of the head and 
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