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ANATOMY AND PHYSIOLOGY § 
entice the males by means of a characteristic odor, emanating 
from the extremity of the abdomen. In lyczenid caterpillars, 
an eversible sac on the dorsum of the seventh abdominal seg- 
ment secretes a sweet fluid, for the sake of which these larve 
are sought out by ants. 
Wax Glands.— Wax is secreted by insects of several orders, 
but especially Hymenoptera and Hemiptera. In the worker 
Ventral aspect of worker honey bee, showing the four pairs of wax scales.—After 
CHESHIRE. 
honey bee the wax exudes from unicellular hypodermal glands 
and appears on the under side of the abdomen as four pairs 
of wax scales (Fig. 102). Plant lice of the genus Schigo- 
neura owe their woolly appearance to dense white filaments of 
wax, which arise from glandular hypodermal cells. In scale 
insects, waxen threads, emerging from cuticular pores, become 
matted together to form a continuous shield over and often 
under the insect itself, the cast skins often being incorporated 
into this waxen scale. The wax glands in Coccide are simply 
enlarged hypodermis cells. 
Silk Glands.—Larve of very diverse orders spin silk, for 
the purpose of making cocoons, webs, cases, and supports of 
one kind or another. Silk glands, though most characteristic 
of Lepidoptera and Trichoptera, occur also in the cocoon- 
spinning larve of not a few Hymenoptera (saw flies, ichneu- 
mons, wasps, bees, etc.), in Diptera (Cecidomyiide ), Neurop- 
