Fore-body 21 



known as prothorax, mesothorax, and metathorax. Each 

 of these segments is regarded as made up of an upper 

 scierite — the notum or tergwn, a lower one — the 

 sternum, and a pair of side pieces — the pleura. In 

 the cockroach, the pronotum is broad and rounded in 

 front ; the head can be drawn in beneath it. It is 

 larger than the two succeeding tergites {mesonotum and 

 metanotum) (see fig. 23). These are pale and thin in 

 the male insect, being covered by the wings. In the 

 female, which has the wings undeveloped, they are 

 hard and brown like the other sclerites. The pro- 

 sternum is narrower than the mesostemum, and the 

 latter is smaller than the metasternum, these sclerites 

 increasing in size from before backwards, like the 

 legs which are associated with them. The meso- 

 stemum is divided into two halves in the female 

 cockroach, as is the metasternum in both sexes. 

 Between each sternum and the insertion of the leg 

 is the pleural part of the segment — two narrow plates, 

 an inner episternum and an outer epimeron (fig. 1 9). 

 Behind each sternum is a small central scierite, the 

 two hinder ones carrying long paired processes (forks) 

 for the attachment of muscles (fig. 17). There is a 

 hollow conical scierite, showing a pit outwardly and 

 a tubular process pointing inwardly towards the 

 body-cavity, in front of the mesosternum, and a 

 similar one in front of the metasternum ; these are 

 apodemes, which, like the forks, serve for the attach- 

 ment of muscles (l). 



In many insects the tergal plates of the fore-body 

 are far more complex than in the cockroach. In the 

 mesonotum and metanotum, four distinct parts placed 

 one behind the other can sometimes be observed ; 

 they are known as the prascutum, scutum, scutellum, 

 and postscutellum (fig. 1 8). The scutellum of the 

 mesothorax is a very conspicuous structure in many 



