524 MEDICAL ENTOMOLOGY 



Although there is no mechanism evident by which the secretion can be 

 expelled, there is no doubt that it is under control, and can be discharged 

 at will when the insect is annoyed or attacked by an enemy. The scent 

 is much more readily perceived by some people than by others, and that 

 of lectularius appears to be more powerful than that of rottindatus. 



DISSECTION OF CIMEX 



The following method of dissecting the bed bug has been found satis- 

 factory. After having killed the insect by placing it in a tube plugged 

 with cotton wool containing a few drops of chloroform, it is taken up with 

 a pair of fine forceps and the legs are pulled off. In removing the fore 

 legs care should be taken not to damage the prothorax. The elytra are 

 next removed by raising them with the forceps and gently twisting them 

 off from their joints at the angles of the mesothorax. The bug is now 

 placed on a slide in a drop of saline solution under a dissecting 

 microscope, with its dorsal surface uppermost, its head directed towards 

 the dissector. With the left hand a fine needle is inserted into the right 

 side of the prothorax, and with another needle in the right hand the joint 

 between the prothorax and mesothorax is separated. By gently drawing 

 on the needle in the left hand and by exerting pressure on the 

 dorsal surface of the abdomen with the other needle, the prothorax is 

 separated from the mesothorax, and the oesophagus, mid-gut and the 

 remaining parts of the intestinal tract are drawn out ; any portion can 

 then be isolated from the rest. The ovoid salivary glands, which lie free 

 in the haematocoele, are readily recognized by their slightly yellowish 

 colour. The cardiac glands lie on each side of the anterior end of the 

 mid-gut. The oesophagus can be followed into the head by slowly 

 picking away the prothorax, and the sucking pump or pharynx can 

 be displayed by breaking up the head ; this is accomplished by first 

 passing a needle through both eyes and then cutting through the sides of 

 the head and reflecting off the dorsal wall ; the pharynx lies on 

 the ventral side. The hind-gut is best dissected out by nicking the last 

 abdominal segment and slowly separating it from the rest of the 

 abdomen ; great care should be taken not to rupture the rectum as it is 

 nearly always full of a black fluid which spoils the preparation. The 

 internal genital organs usually come away together with the rectum. 

 The best way to dissect out these organs is to place the bug in the 

 dissecting trough and to fix it by passing a pin through each side of the 

 prothorax ; the abdominal segments are now nicked along their borders 



