THE INTERNAL ANATOMY OF INSECTS 



97 



Fig. 109. — Head of 

 Melajnplus, cau- 

 dal aspect. 



articulation of the maxilla (Fig. 48). In the Acridiidae (Fig. 109) 

 these apodemes bear a striking resemblance to the lateral apodemes 

 of the thorax (Fig. 106), except that the ventral process of the maxil- 

 lary apodeme is much more prominent, and the two from the opposite 

 sides of the head meet and coalesce, thus forming 

 the caudal part of the body of the tentorium. 



The anterior arms of the tentorium. — Each anterior 

 arm of the tentorium (Fig. 107, 108, no, at) is an 

 invagination of the body-wall which opens on the 

 margin of the antecoxal piece of the mandible 

 when it is distinct ; if this part is not distinct the 

 apodeme opens between the clypeus and the front 

 (Fig. 46, at). 



The dorsal arms of the tentorium. — Each dorsal 

 arm of the tentorium arises from the side of the 

 body of the tentorium between the anterior and posterior arms 

 and extends either to the front or to the margin of the antennal 

 sclerite (Fig. 107, 108, no, dt). 



The frontal plate of the tentorium. — In the cockroaches the anterior 

 arms of the tentorium meet and fuse, forming a broad plate situated 

 between the crura cerebri and the mouth ; this plate was termed by 

 us the frontal plate of the tentorium (Fig. 107,/^). On each side, an 

 extension of this plate connects it with the body of the tentorium; 

 these enclose a circular opening through which pass 

 the crura cerebri. 



Other cervical apodemes and some chitinized 

 tendons are described in the paper cited above. 



The endothorax. — The internal skeleton of the 

 thorax is commonly termed the endothorax; under 

 this head are not included the internal processes of 

 the appendages. 



The endothorax is composed of invaginations of 

 each of the sections of a thoracic ring. Those por- 

 tions that are derived from tergites are termed 

 phragmas; those derived from the pleurites, lateral 

 apodemes; and those, from the stemites, furcce. 



The phragmas. — A phragma is a transverse partition extending 

 entad from the front or the hind margin of a tergite ; three of them 

 are commonly recognized; these were designated by Kirby and 

 Spence (1826) the propkragma, the mesophragma, and the meta- 

 phragma; but, as they do not arise one from each segment of the 



Fig. I 10. — Ten- 

 torium of Mela- 

 nopliis, cephalic 

 aspect. Thedistal 

 end of the dorsal 

 arms detached. 



