136 OUR HOUSEHOLD INSECTS 



of such a medium. We will suppose the insect to have 

 been pinned down to its support in its natural posi- 

 tion ; then, on slitting open the skin along the middle 

 of the back with a pair of fine-pointed scissors, a mass 

 of whitish substance is revealed, which, by its extent 

 and opacity, obscures all the chief organs of the body. 

 This is the " fat body," and must be removed before the 

 digestive apparatus can be properly seen. It may be 

 gently pulled out piece by piece. When this is done, 

 the digestive system is seen to occupy the greater part 

 of the cavity of the body, most of it being situated in 

 the abdomen. 



The hinder wall of the cavity of the mouth forms a 

 raised fleshy organ, called the lingua, which assists in 

 taking in the food. At the hinder end of this the throat 

 contracts into a narrow tube, the cesophagus, which 

 passes back through the thorax, and gradually expands 

 into a capacious pear-shaped bag with thin walls, called 

 the crop. So gradual is the enlargement from oesophagus 

 to crop, that it is impossible to say where the one ends 

 and the other begins. The crop is the receptacle which 

 receives the multifarious objects of the cockroach's diet, 

 after they have been roughly chewed, or rather chopped 

 up, by the mandibles. It is really of enormous size, 

 considering the dimensions of the insect, and its capacity 

 affords a very good measurement of the voracity of its 

 possessor. At its further extremity the crop suddenly 

 narrows, and is immediately succeeded by another and 

 very much smaller pear-shaped body, set the other way 

 round, i.e., with its large end foremost and narrowing 

 behind. It has thick muscular walls, and is furnished 

 inside with a circle of six large chitinous prominences 

 called teeth, as well as with little cushion-like bodies set 

 with hairs. The whole organ is called the gizzard. 



