96 



AN INTRODUCTION TO ENTOMOLOGY 



Fig. 1 06. Ental surface of 

 the pleurites of the meso- 

 and met.athorax of Melano- 

 plus, showing the lateral 

 apodemes, ap, ap. 



Frequently, in the more generalized insects, the mouth of an apodeme 

 remains open in the adult insects. In Figure 106 are represented two 

 apodemes that exist in the thorax of a 

 locust, Melanoplus. Each of these (ap 

 and ap) is an invagination of the body- 

 wall, between the episternum and the 

 epimeron of a segment, immediately 

 above the base of a leg. These are known 

 as the lateral apodemes of the thorax and 

 serve as points of attachment of muscles. 

 The number of apodemes may be very 

 large, and it varies greatly in different 

 insects. Among'the more important apo- 

 demes are the following: 



The tentorium. The chief part of the internal skeleton of the 

 head is termed the tentorium. This was studied by Comstock 

 and Kochi ('02). We found that in the generalized insects studied 

 by us it is composed of two or three pairs of apodemes that, extend- 

 ing far into the head, meet and coalesce. The three pairs of 

 apodemes that may enter into the formation of the tentorium 

 were termed the anterior, the posterior, and the dorsal arms of the 

 tentorium respectively. The coalesced and more or less expanded 

 tips of these apodemes constitute the body of the tentorium. From 

 the body of the tentorium there extend a variable number of processes- 

 or chitinized tendons. 



The posterior arms of the tentorium. The posterior arms of the 

 tentorium (Fig. 107, 109, no, pt) are the lateral apodemes of the 



At 



Fig. 107. Tentorium 

 of a cockroach, dor- 

 sal aspect. 



Fig. 1 08 .Part of the 

 tentorium of a cric- 

 ket, ventral aspect. 



maxillary segment. In many Orthoptera the open mouth of the 

 apodeme can be seen on the lateral aspect of the head, just above the 



