NORTH AMERICAN CADDIS-FLY LARVE. 
first and second thoracic segments are chitinized dorsally, and the 
third segment bears three pairs of chitinous plates. 
The Head.—The head is generally oval, sometimes decidedly 
tapering toward the mouth parts. The gula is triangular or elon- 
gate, and the epicrania are contiguous, or nearly so, behind its base. 
The labrum is broader than long, variously armed with bristles and 
hairs. ‘The mandibles are stout, with blunt rounded teeth, and a 
pair of sete on the outer surface and a brush on the inner surface. 
The Thorax.—The dorsal surface of segments 1 and 2 is com- 
pletely covered by chitinous shields. On the ventral surface of 
the prothorax there is usually a slender curved “horn” directed for- 
ward between the bases of the forelegs. The metathorax is soft, 
except for three pairs of chitinous plates; of these the lateral pair 
is somewhat crescentric in form and occurs slightly above the bases 
of the metathoracic legs; the median pair is small and somewhat 
oval or triangular, and is located near the cephalic margin of the 
segment; the second pair is small and of varying form, and is 
located more laterally and posteriorly than the median pair. 
The Abdomen.—The abdomen is cylindrical in cross-section 
and of nearly uniform diameter throughout its length. Its first 
segment is provided with three more or less perfectly developed 
“spacing-humps” or callous spots. Gills are always present, but 
vary greatly in number and arrangement; they occur on the first 
segment, so far as known, only in an unidentified species of the 
genus Limnophilus. The lateral fringe is present, but is sometimes 
very feeble. The last segment bears a chitinous plate on the dorsal 
surface. The first segments of the prolegs are fused to form an 
apparent tenth segment. 
DESCRIPTION OF THE CasE.—The larve of the various genera 
of the Limnophilidz make cases of great variety of form, and of 
almost every obtainable material. 
In spite of their great variety of form and material the cases 
can, with a few exceptions, be readily determined by an observer 
with a little experience. 
To this family belong the log-cabin type of cases; the cylin- 
drical cases with little or no taper, made of rough fragments of 
bark, or sticks, or leaves, shells, or seeds ; the cylindrical cases with 
heavy ballast sticks at the sides ; also cases made of leaf fragments 
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