38 



THE COCKROACH : 



The sides of the head are completed by the eyes and the 

 genge. The large compound eye is bounded above by the 

 epicranium ; in front by a narrow band which connects the 

 epicranium with the clypeus ; behind, by the gena. The gena 

 passes downwards between the eye and the epicranial plate, 

 then curves forwards beneath the eye, and just appears upon 

 the front of the face, being loosely connected at this point with 

 the clypeus. Its lower edge overlaps the base of the mandible, 

 and encloses the extensor mandibulsB. 



The occipital foramen has the form of an heraldic shield. Its 

 lateral margin is strengthened by a rim continuous with the 

 tentorium, or internal skeleton of the head. Below, the fora- 

 men is completed by the upper edge of the tentorial plate, 



Fig. 16. Back of Head, ca, cardo ; st, stipes ; ga, galea ; la, lacinia ; pa, palp ; 

 sm, subrnentum ; ra, nientum ; pg, paraglossa. X 10. 



which nearly coincides with the upper edge of the submentum 

 (basal piece of the second pair of maxillce) ; a cleft, however, 

 divides the two, through which nerve-commissures pass from 

 the sub-cesophageal to the first thoracic ganglion. Through the 

 occipital foramen pass the oesophagus, the salivary ducts, the 

 aorta, and the tracheal tubes for the supply of air to the head. 



The internal skeleton of the head consists of a nearly trans- 

 parent chitinous septum, named tentorium by Burmeister, which 

 extends downwards and forwards from the lower border of the 



