184 PEACTICAL PARASITOLOGY 



segment. In the middle of the ventral surface, a prolongation of the 

 mesothorax runs back between the hind legs and covers the stink- 

 glands, the secretion from which gives to bugs their characteristic 

 odour. 1 The thin metathorax is almost completely covered by the 

 rudimentary wings. 



As in other Insecta, the legs of the bug are divided into coxa, 

 trochanter, femur, tibia, and tarsus. The latter is three-jointed and 

 possesses two claws. The distal end of each tibia is furnished with a 

 bristle. 



The abdomen is rounded at the sides and runs off to a point 

 at the back ; it is divided into eight segments. The hindermost 

 bears the anus, which is oval in shape, is placed transversely, and 

 is surrounded by a chitinous ring. From it two thin-skinned, tongue- 

 shaped appendages may be protruded, one dorsally and one ventrally. 

 In the male, the hindermost segment also bears the genital opening, 

 which is situated in front of the anus and is associated with the 

 claw-shaped penis, which is usually folded towards the right. The 

 genital opening in the female is a simple longitudinal slit upon 

 the ventral surface of the seventh segment. At the sides of this 

 segment are two thin, wing-shaped processes, directed posteriorly. 



All the abdominal segments, with the exception of the eighth^ 

 are furnished with two stigmata, placed one upon each side upon 

 the ventral surface ; an eighth pair, which is very difficult of detection, 

 is situated upon the anterior edge of the metathorax. 



The rostrum, when in repose, is always bent towards the ventral 

 surface; it is a four-jointed tube, tapering towards the free end, 

 within which is another and thinner tube. The outer tube, or sheath, 

 consists of .two parts ; while the inner tube, or scalpel, is composed 

 of four. The sheath is made up of the labium, or lower lip, and the 

 labrum, or upper lip, while the mandibles and maxillae go to form 

 the scalpel. It is possible to dissect out these parts, but, owing to 

 their small size in the bed-bug, the manipulation is a difficult one. 

 Among a large number of prepared specimens, however, there will 

 always be one or two in which the component parts of the organ, 

 while remaining attached to the head, are yet separated from one 

 another. It will then be seen that the principal portion of the sheath, 

 formed by the labium, is a long tube, tapering towards the distal end, 

 and in the ventral wall of which, close to the head, is an aperture. 

 This aperture is closed by the labrum, which is modified into a 

 tongue-shaped process. 



From the sheath project the divergent tips of the mandibles 



1 Young insects possess abdominal stink-glands until they slough for the last 

 time. Their thoracic segments, moreover, increase in size from front to back. 



