INTRODUCTION. 
ceridz, as discussed under that family, there are variations of the 
trochanter.) (3) The Femur, usually broad and _ flattened. 
(4) The Tibia. (5) The Tarsus, which is a single segment bear- 
ing a large claw, usually armed with a tooth. 
Gills rarely occur on the thorax. 
The Abdomen.—The abdomen consists apparently of ten seg- 
ments, or apparently of nine segments. All of the segments, ex- 
cept the last, are entirely membranous, except a few Hydroptilide 
which bear small chitinous plates on certain segments, and a few 
other forms that have some small ventral plates. The first segment 
in the case-building forms often bears three “spacing-humps,” or 
tubercles. These tubercles are mound-like elevations of the integu- 
ment that serve to keep a space between the insect and its case for 
the free circulation of the respiratory currents of water. They are 
peculiar to the order Trichoptera. One tubercle is located on the 
middorsal surface of the segment. It often terminates in a mova- 
ble, nipple-like process. The other two tubercles, the lateral humps, 
are situated on the sides of the segment and always end obtusely. 
On the ventral surface of the segment the cuticula is sometimes 
raised into a lip-like fold, or it may be entirely flat. It is provided 
with numerous sete, which are arranged in definite order and 
often provide convenient means of classification. Some of the 
segments between the first and the last, of the case-building caddis- 
worms, usually bear a “lateral fringe,” or “lateral line.” This is 
a continuous line of delicate hairs, often situated on a fold of the 
cuticula, which undulate in a wave-like manner from front to 
rear, and keep a continuous flow of fresh water passing through 
the case. 
Gills, when present, most commonly occur on the abdomen, 
where they may be situated near the front or hind margin, or near 
the middle of the segment. They are always filamentous, but they 
may arise in tufts or singly, they may be branched or unbranched. 
Regardless of their location in respect to the cephalic and caudal 
margins of the segments, they are always arranged in rather defi- 
nite lines known as: (1) The Lateral Series, which is located near 
the mid-lateral surface of the body. (2) The Sub-dorsal Series, 
which is located above the lateral series, just below the dorsal sur- 
face of the body. (3) The Sub-ventral Series, which is located 
below the lateral series, just above the ventral surface of the body. 
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