LIBRARY

410
Larva
COLLEGE ENTOMOLOGY
INTERNAL ANATOMY
Adult
1 nternal anatomy quite thoroughly studied. Internal anatomy of adult not extensively
known.
Alimentary canal distinctly divided into Alimentary canal somewhat shortened.
fore intestine, mid-intestine, and hi?d Stomach small.
intestine. Surface of mid-intestine wlth
transverse folds.
Two pairs of salivary glands·
Intestine partly coiled.
Six Malpighian tubes Six Malpighian tubes
Silk glands very large, occupying much of Silk glands-modified during pupation inthe
anterior portion of the body. Spin- to salivary glands in the imago.
neret situated on the middle of the front
margin of the labium.
Accessory excretory organs, known as Gilson'a
glands, occur in many species.
Cephalic, tIn'ee thoracic, and six to eight Cephalic, three thoracic, and seven ababdominal
ganglia. dominal ganglia.
Respiration through the integument or by Spiracular and tracheal respiration.
means of gills.
The eggs are loosely deposited in transparent gelatinous masses or strings
in the debris at the bottom of water courses or attached to rocks, roots, logs,
and aquatic plants. Upon hatching, most of the eruciform larvre begin to can.
struct characteristic cases which are enlarged as needed. Some species make
very simple cases on stones, others spin elaborate ones from many kinds of
materials. but usually each species adheres to a more or less definite pattern;
a few burrow holes in bits of wood in which they are concealed and still others
live in loose bag-like or funnel-shaped webs which are attached at the anterior
end and suspended loosely in the current. Those building the movable cases
attach themselves to the posterior end of their abodes by means of the caudal
prolegs. They allow only the armored head, thorax, and legs to protrude when
swimming, feeding, or dragging their cases about, and withdraw entirely into
the same at will. Thus it is that one often sees small bits of sticks, leaves, and
peculiar forms of pebbles, sand, and other shapeless objects moving on the
bottoms in a slow jerky fashion. Species living in swift waters often construct
loosely woven bags or funnel-shaped abodes, attached only at the anterior end
and kept inflated and in constant motion by the current. The campodeiform
larvre either live unprotected in the debris or build more stationary abodes,
supplemented by catching nets which screen out food for the occupant. Often
the stationary cases are constructed in a series close together, but not usually