STRUCTURE OF THE BODY-LOUSE 17 



becomes the rectum (Fig. 3, 13), on which is a 

 swollen portion or ampulla (Fig. 3, 12), which 

 has a thick wall and apparently expels the faeces. 

 The rectum opens to the exterior at the anus 

 (Fig. 3, 14), which is at the end of the body. 

 There are two pairs of salivary glands, which 

 are always prominent organs in insects, their 

 secretion having a wider scope than that of the 

 organs of the same name in mammals. One 

 pair are trouser-shaped (Fig. 3, 7) and lie on the 

 fore-gut, closely attached to its surface. The 

 other pair are kidney-shaped (Fig. 3, 8) and lie 

 on either side of the oesophagus. Each of the 

 four is connected with the pipe of the stabber 

 by means of a very fine duct (Fig. 3, 9), which 

 carries away the secretion. 



The nervous system consists of three central 

 masses, from which the nerves run to the various 

 organs they serve. These are, firstly, a large 

 mass or brain (Fig. 3, 15) which lies in the head 

 above the oesophagus ; secondly, a smaller mass 

 (Fig. 3, 16) lying below the stabber base and 

 connected with the brain by means of a nerve 

 cord on each side running round the gut ; thirdly, 

 a large mass (Fig. 3, 17) lying in the thorax below 

 the gut, and from which nerves run to the legs 

 and backwards into the abdomen. This third 

 mass is connected by a nerve cord with the 

 second. 



The louse, like all other insects, breathes 

 through a system of tubes, or tracheae, which are 



c 



