GENERAL EXTERNAL STRUCTURE OF INSECTS. 



21 



Emp' 



Fin. 5. — Tyiiiral insect 



stei^ellur)% (SI), and poxtxtcrncllnm (Psl). In some of the lower 

 insects a plate (,») occurs at each side of the presternum or of the 

 sternum which seems to fall in line with the preepisternum of the 

 l^leurum. This has been variously called a jxirt of the /n-esternum, 

 the coxoste/'fiuni, an accessory stomal plate, and the sternal laterale. 

 The inner surface of the 

 sternum carries a large 

 two- pronged process 

 called the furca or ento- 

 sternuni. 



This plan of structure 

 for the mesothorax and 

 the metathorax prevails 

 throughout all insects. 

 The honey bee probably 

 presents the greatest de- 

 parture from it, but even 

 l.>ere the modification consists principally of a suppression of the 

 sutures of the pleurum resulting from a condensation of the parts. 



The leg (fig. 5) of an adult insect consists of a number of joints 

 or segments. It is attached to the body, as just described, by a thick 



specimens. In such iireparations, liowovev, one finds that there are in most 

 cases two sclerites here instead of one, and, fnx'thermore, that one or occa- 

 sionally two others are similarly situated beneath the rear part of the wing 

 base behind the pleural wing process. The present writer has. therefore, 

 made the term " paraptera " cover this whole row of little plates, distinguish- 

 ing those before and those behind the pleural wing process by the designations 

 given above. 



In the latter part of Audouin's definition it would seem that he may have 

 confused the rudimentary tegula as it exists in some insects with the parapte- 

 rum, but eA'en this is not probable since he says it is always connected with 

 the episternum, which is never true of the tegula. In his description of the 

 thorax of beetles, Dijtiscus, Carabus, Buprestis, and CurcuJio, it is evident 

 that he regards the anterior upper part of the episternum as the parapterum 

 fused with the latter plate. In fact, In each case he definitely states that such 

 is the case and, in describing DuUscus circumflcriis, he says (p. 420) : "The 

 episternum, the parapterum, and the epimerum all fuse dorsally and constitute 

 a support for the wings and tergum." While Audouin is undoubtedly mis- 

 taken in this homology, especially in the mesothorax, he at least shows that 

 his " paraptere " is a part of the pleurum. Hence modern writers such as 

 Packard and Folsom who make the term " paraptera " synonymous with 

 " teguliiE' " are certainly wrong. The tegula is a dorsal scale or its rudiment 

 at the humeral angle of the wing, while the parapterum is a co-existent scle- 

 rite below this part of the wing base. The present writer agrees with Comstock 

 and Kellogg, who, in their Elements of Insect Anatomy (first edition), define 

 the little sclerite in front of the l)as(' of the wing in the locust, articulated to 

 the dorsal extremity of the episternum. as the '• parapteron," though in this 

 insect there are here really two of these paraptera 1 plates instead of one. 



