THE INSECTA 151 



organs which are not present in any other arthropods. Taking 

 the several regions of the body in some detail, the head is 

 relatively small, elongated dorso-ventrally, and compressed from 

 front to back. Viewed from in front it has a somewhat pear- 

 shaped outline, the upper part being broad, and evenly rounded, 

 while the sides narrow downwards towards the mouth. The 

 whole of the front and sides of the head are defended by 

 strong chitinous plates namely, two epicranial plates covering 



Fig- 36 



The head of Periplaneta, orientalis seen from in front, ant, 

 antenna ; dp, clypeus ; , eye ; ep, epicranium ; es, epi- 

 cranial suture ;fe, fenestra ; Ibr, labrum ; lp, labial palp; 

 md, mandible ; ;;//, maxillary palp. 



the dorsal and posterior sides ; a clypeus, forming the lower 

 part of the face ; the genae, a pair of plates covering the sides of 

 the head below the eyes. The labrum or upper lip is an oblong 

 plate hinged on the lower edge of the clypeus. The arrange- 

 ment of the plates is shown in fig. 36. The head bears a 

 pair of large compound eyes, a single pair of very long filiform 

 antennae, and three pairs of foot-jaws viz. the mandibles and 

 two pairs of maxillae. The eyes are large reniform swellings at 

 the sides of the head, the surface of each being divided into a 



