EXTERNAL CHARACTERS 



155 



2. The neck is short and slender : its cuticular covering 

 is soft and white, with the . exception of seven 

 thickened patches or sclerites which are hard and 

 brown. Of these sclerites two are slender transverse 

 bars on the ventral surface ; a third is median and 

 dorsal, and almost divided into two longitudinally ; 

 the remaining four are much larger, and form two 

 pairs at the sides of the neck. 



EiG. 36.— Periplaneta Americana. The head, front view, (c.h.h.) 



A, antenna. CL. clypeua. E, eye. EP, epicranium. F, fenestra. Q-, galea. 

 GE, gena. Xi, lacinia. XiF, labial palp. XjH, labrum. MiN*, mandible 

 (the left mandible has been removed). MP, maxillary palp. M2, second 

 maxilla. 



EiG. 37. — Periplaneta Americana. The head from behind, (o. h. h.) 



E, EP, G, L, LP, Mlf, and MP as in the preceding figure. 



O, oardo. LG, ligula. M, mentum. K", nerve-connective. O, oesophagus. 

 PG, paraglossa. S, stipes. SD, salivary ducts. SM, submentum. TE, 

 vical trachese. 



3. The thorax consists of three segments. 



a. The prothorax is the first and longest segment of 



the thorax. Its tergum, the pronotum, is pro- 

 longed forwards over the neck. 



b. The mesothorax is smaller, and its tergum bears at 



its anterior corners a pair of elytra, or wing-covers. 



