PARASITES OP ANIMALS. 33 



free, being hollow, thin bands of chitine, meeting like the 

 maxillas, 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 

 Figure 28. ^ drawing blood. On the other hand, the 

 maxilla3, 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 maxilla?, 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. Bed-bug (Cimex leetularius Linn.), enlarged. The straight line 

 shows the ordinary length. From Packard's Guide. 



5 



