THE EXTERNAL ANATOMY OF INSECTS 



53 



into the composition of this division when it consists of more than 

 a single sclerite. To meet this difficulty Snodgrass has proposed 



that the term eusternum 

 be applied to the sclerite 

 that has been known as 

 the sternum; and that 

 the word sternum be 

 used only to designate 

 the entire ventral divi- 

 sion of a segment. 



C. THE ARTICULAR 



SCLERITES OP THE 



APPENDAGES 



Fig. 64. — Prothorax of Penthe; c, coxaj cc, coxal 

 cavity; /, femur; 5, prosternum; <r, trochanter. 



At the base of each leg 

 and of each wing there 

 are typically several 

 sclerites between the appendage proper and the sclerites of the trunk 

 of the segment ; these sclerites, which occupy an intermediate position 

 between the body and its appendage, are termed the articular sclerites. 



Frequently one or more of the articular sclerites become consoli- 

 dated with sclerites of the trunk so as to appear to form a part of its 

 wall; this is especially true of those at the base of the legs. 



The articularscleritesof thelegs. — ^The proximal segment of the leg, 

 the coxa, articulates with the body by means of two distinct articula- 

 tions, which may be termed the pleural articulation of the coxa and the 

 ventral articulation of the coxa respectively. The pleural articulation 

 is with the ventral end of the foot of the lateral apodeme of the seg- 

 ment, i. e. with the pleural coxal process, which is at 

 the ventral end of the suture between the epistemum 

 and the epimerum (Fig. 6 1 , CxP) . The ventral arti- 

 culation is with a sclerite situated between the coxa 

 and the epistemtim; this sclerite and others asso- 

 ciated with it may be termed the articular sclerites 

 of the legs. The articular sclerites of the legs to 

 which distinctive nameS have been applied are the 

 following : 



The trochantin. — The maximum number of 

 articular sclerites of the legs are found in the more 

 generalized insects; in the more specialized insects 

 the nvimber is reduced by a consolidation of some of them with 



Fig. 65.— The 

 base of a leg 

 of a cock- 

 roach. 



