ANATOMY OF AN AKTHEOPOD. 



101 



those of the head, which are firmly fused together. This 

 segmentation of the exoskeleton is seen, internally, in the 

 muscular and nervous systems. 



On examining the cockroach (fig. 38), which belongs to an 

 order of Hexapoda known as the Orthoptera, we shall at once 

 notice that the whole body is divided into three parts — the 

 head {H), the thorax or chest region {Th), and the abdomen 

 {Ab). The head is loosely connected with the thorax by a 



Fiii. 3i). — A, Head, and e, Lower Lip of Cockroach. 



narrow isthmus of tissue, the neck. The head is broad, and 

 the mouth, which bears biting jaws, is on the lower portion. 

 The jaws will easily be seen to work sideways or transversely, 

 and not vertically as ours do. Situated on the head are two 

 large, black, reniform elevations, the eyes [E), one on each 

 side. These are the compound eyes, each being composed of 

 a number of hexagonal facets. Situated at the inner side of 

 the bases of the feelers or antennfe are two small white patches, 

 the so-called /eraesij-ce (fig. 38,/, and fig. 39 a, F). The antennse 

 or jointed feelers spring from the base of the eyes in a de- 

 pression on their anterior edge. The dorsal and posterior 

 surface of the head is called the epicranium (Ep). Below the 



