572 



ZOOLOGY 



of its generalised structure, which - makes it a fairly central 

 member of the class, devoid of any extreme modifications. 



Three regions are very distinctly recognisable in the body of 

 the Cockroach. In front is the head, elongated vertically, bearing 

 the very long slender feelers and the large eyes, and contracted 

 behind to form a narrow neck. In the middle is the thorax, 

 consisting of three segments bearing the three pairs of legs and 

 the two pairs of wings. Behind is the abdomen, consisting of ten 

 segments covered over above by the wings. The entire surface 

 is covered by a chitinous cuticle, which is specially thickened on 

 the head, on certain parts of the thorax, and in the anterior pair 

 of wings. 



The head consists of four parts -the epicranium behind, com- 

 prising the region between and behind the eyes, and the clypeus, 



FIG. 453. Periplaneta americana. Male, dorsal view. Natural size. 



or portion extending vertically downwards, with two latert 

 parts, the gence, in front. The eyes are a pair of reniform blacl 

 patches on the sides of the head ; each is seen when examined 

 with a lens to be divided into a number of minute hexagonal am 

 or facets, like those in the eye of the Crayfish. Borne in sockel 

 just below the eyes are throng, slender, highly mobile feelers o 

 antennae, each made up of SRrge number of short segments, the 

 first three being larger than the others. Internal to the base if 

 each antenna is a rounded white space the fenestra the nature 

 of which is not known, but which may be an abortive representa- 

 tive of the simple eyes or ocelli found in most Insects. 



Movably articulated with the lower or ventral end of the 

 clypeus is jfltepad plate, the labrum or upper lip (Fig. 454, Ibr.} 

 overhang nil aperture of the mouth. Below the gena3 am 

 articulatinP ((rch the sides both of the epicranium and clypeus 



