XI 



PHYLUM ARTHROPODA 



621 



JILX 



the gencc, in front. The eyes are a pair of reniform black patches 



on the sides of the 



head ; each is seen 



when examined with a 



lens to be divided into 



a number of minute 



hexagonal areas or 



facets, like those in the 



eye of the Crayfish. If me 



Borne in sockets just 



below the eyes are the 



long, slender, highly 



mobile feelers or an- 



tennce, each made up 



of a large number of 



small segments, the 



first three being larger 



than the others. In- 

 ternal to the base of 



each antenna is a 



rounded white space 



the fenestra the 



nature of which is not 



known, but which may 



be an abortive repre- 

 sentative of the simple 



eyes or ocelli found in 



most Insects. 



Movably articulated with the lower or ventral end of the 



clypeus is a broad plate, the labrum or upper lip (Fig. 492, Ibr.) 



overhanging the aperture of the 

 mouth. Below the gena3 and arti- 

 culating with the sides both of the 

 epicranium and of the clypeus are a 

 pair of stout mandibles (Fig. 492, 

 md., and 493, man.) which work 

 horizontally like those of the Cray- 

 fish ; their inner edges are divided 

 into a number of teeth. Behind 

 the mandibles are a more flexible 

 pair of jaws the first pair ofmaxillce 

 (mx. 1 , max. 1 ). Each maxilla exhibits 

 a structure comparable to the funda- 



mpn t{,l fvrP nf rliP armpnrtao-p^ nf 

 "jP* a PP ( UagC 



the Crayfish : a basal part or proto- 



. * . . 



pOCllte, Consisting 01 tWO Segments 

 i i 



(podomeres), supporting an internal 



mx, 



FIG. 402. Mouth parts of the Cockroach Ibr. labrum ; 

 in. mentum ; md. mandible ; m.i: 1 . anterior pair of maxilla' ; 

 me. and mi. outer and inner divisions of the first and 

 second pair of maxillaj ; mx*. second maxilfce; pi. labial 

 palp ; pin. maxillary palp ; st. stipes ; sm. submentum. 

 (From Lang's Comparative Anatomy.) 



FIG. 493. Periplaneta axnericana. 



Lateral view of the head and its ap- 

 pendages, cerv. one of the cervical 

 sclerites ; cy. eye ; gen. gena ; man. 

 mandible ; max 1 ., first pair of max- 

 illa; ; max*, second pair of maxilla? 



