PARASITES OF ANIMALS. 83 
free, being hollow, thin bands of chitine, meeting like the 
maxille, or tongue, of butterflies, to form a hollow tube for suc- 
tion. The mandibles each suddenly end in a curved, slender 
filament, which is probably used as a tactile organ to explore 
the best sites in the flesh of their victim for 
drawing blood. On the other hand, the 
maxilla, which are much narrower than the 
mandibles, become rounded toward the end, 
bristle-like, and tipped with numerous ex- 
ceedingly fine barbs, by which the bug 
anchors itself in the flesh, while the blood is 
pumped through the mandibles. The base 
of the large, tubular labium, or beak, which ensheathes the 
mandibles and maxillee, is opposite the end of the clypeus, or 
front edge of the upper side of the head, and at a distance 
beyond the mouth equal to the breadth of the labium itself. 
The labium, which is divided into three joints, becomes flat- 
tened toward the tip, which is square, and ends in two thin 
membranous lobes, probably endowed with a slight sense of 
touch.’ At the same time that the blood is sucked up, some 
poisonous secretion or saliva is introduced into the wound, 
perhaps to render the blood more liquid. ‘To some persons 
these bites are extremely poisonous and cause large inflamed 
swellings and violent itching, while in other persons no such 
effects occur, and the bites are scarcely noticed. 
These insects are inclined to be gregarious in their habits, 
and are fond of herding together, a dozen or more in aplace, 
’ whether in a crack, knot-hole, chink in the walls of houses, or 
any snug corners about a bedstead. They are also fond of 
returning constantly to the same hiding-place, morning after 
morning, after their nocturnal raids, just as many birds re- 
turn regularly to their roosts. On this account their retreats 
become discolored by dark spots of excrement. When 
much disturbed, or when food fails, they will disperse, how- 
ever, and each one will migrate on its own account. In the 
night they are quite lively and nimble, and run about with 
Figure 28. 
Figure 28.—Bed-bug (Cimex lectularius Linn.), enlarged. The straight line 
shows the ordinary length. MWydincRackarit's Gatide. 
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