NORTH AMERICAN CADDIS-FLY LARVZ. 
back in a narrow line. On the metathorax the median chitinous 
plates are almost contiguous; the lateral plates are somewhat cre- 
centric in form, and have a sparse growth of black sete near the 
cephalic end. 
The Abdomen.—On the first segment the dorsal hump is lack- 
ing; the lateral humps are well developed. The dorsal surface of 
the segment has a sparse growth of black setee, which are not ar- 
ranged in groups; the ventral surface of the segment bears a pair 
of light-colored chitinous plates, one each side of the median line 
behind the middle of the segment, each plate bearing a sparse line 
of short, dark-colored sete along its cephalic margin; in front of 
these plates the cuticula bears a few irregularly placed sete; at 
the base of each lateral hump, on the ventral side there is a pair 
of pale chitinous plates, the caudal plate the larger, each bearing 
a few sete. The distribution of gills is represented in figure 76. 
DescCRIPTION OF THE CAseE.—The species makes such a great 
variety of cases, of which different types so closely resemble the 
cases made by several other genera, that it is impossible to place 
any taxonomic importance on their architecture. 
In a rough way the cases fall into two types—circular and 
triangular in cross section. 
The triangular cases, made like the caudal part of figure 78, 
show the most distinct plan of architecture. From the exterior 
three sides are visible; each side is slightly convex, and is made 
of from three to six roughly oval sections of dead leaves. The 
cephalic end of each oval is fastened under the caudal end of the 
preceding oval. In cross section, figure 75, it is apparent that the 
outer triangle surrounds a thin-walled cylinder of leaf fragments, 
lined with silk. 
In the cylinder type of case the larvee sometimes make very 
neat structures of flat chips of stones, figure 72. In these cases 
the stone chips are neatly fitted and cemented together with a thin 
lining of silk. In cross section the cases are as nearly cylindrical 
as the size of the stones will permit. Besides these cases, which 
are built with a high degree of neatness, the larvae sometimes make 
cases of twigs, fragments of bark, and debris of all sorts. These 
cases, of which figure 77 represents one of the most perfect, are 
among the most slovenly and carelessly-built cases inhabited by 
Limnophilade. 
56 
