COCKROACH. 



313 



Nervous system. A pair of supra-cesophageal or cere- 

 bral ganglia lie united in the 

 head. As a brain they receive 

 impressions by antennary and 

 optic nerves. By means of a 

 paired commissure surround- 

 ing the gullet, they are con- 

 nected with a double ventral 

 chain of ten ganglia. Of 

 these, the first or sub-cesopha- 

 geal pair are large, and give 

 off nerves to the mouth-parts, 

 etc. ; from each of the ganglia 



Of the thorax and the abdO- 



FIG. 153. Leg of cockroach. 



rr 



men nerves are given off to 



Mn. 



, Broad expanded coxa; fr., troch- 

 anter;_/C, femur; ti., tibia; ta., rive- 

 jointed tarsus with terminal claws and 

 adhesive cushions. 



adjacent parts. There are 



three pairs of ganglia in the thorax, and six in the abdo- 

 men, of which the last is the largest. From the cesophageal 



commissures two vis- 

 ceral nerves are given 

 off, which form in a 

 somewhat complex man- 

 ner the innervation of 

 gullet, crop, and gizzard. 

 Besides the large com- 

 pound eyes, there are 

 other sensory structures 

 some of the hairs on 

 the skin, the maxillae 

 (to some extent organs 

 of taste), the antennae 

 (tactile and olfactory), 

 the anal cerci (tactile), 

 and possibly the oval 

 white patches on the 

 head. 



Alimentary system. 

 - (i) The fore - gut 

 (stomodseum) is lined 

 by a chitinous cuticle continuous with that of the outer 

 surface of the body. It includes (a) the buccal or mouth 





II 



, m 



\v 



III 



FIG. 154. Mouth appendages of cock- 

 roach. After Dufour. 



I. J/;*., mandibles ; II. first maxillae ; C., cardo ; 

 St., stipes; Z,., lacinia ; G., galea ; mx.p., 

 maxillary palp ; III. second maxillae or la- 

 bium ; S.m., submentum; ;;/., mentum ; L.. 

 laciniae ; p.g., paraglossa ; /./., labial palp. 



