52 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [Bull. 



j)leuron. is called the liypopleura in his terminolog-y. As he states 

 (p. 498), this terminology is a purel}^ conventional one which "offers 

 more chance of fixity: it may very well exist alongside of a homolog- 

 ical and anatomical terminology" which is "often subject to uncer- 

 tainty and disj)ute." While this objection to applying a standard 

 terminology to the thoracic sclerites of the Diptera may have been a 

 valid one at that time, in the half century which has intervened, the 

 homologies of the sclerites of the dipterous thorax have been establish- 

 ed quite satisfactorily, and it is no longer necessary for dipterists to 

 employ a terminology of their own (and differing from that used 

 in the other orders of insects) in referring to the venation of the 

 Avings. or to the sclerites of the thorax. 



The anepisternum, aes of Fig. 6, A, B and I) (called the ")neso- 

 pleura" by Osten-Sacken), is only the upper portion of the epister- 

 num, although it is usually interpreted as the entire episternum in 

 the Diptera. It is separated from the mesonotum and the prothorax 

 by a membranous area in many lower Diptera (Fig. 6, A and B), but I 

 in the higher Diptera (Fig. 6, C and E) it encroaches upon the mem- I 

 branous region above it as far as the dorsox)leural or notopleural 3 

 suture, and extends forward to the prothorax, with which it becomes 4 

 rather closely united as far as the region of the anterior spiracle. ,| 

 Its posterior boundary is marked by the pleural suture, ps; and its 

 ventral boundary is marked by the anepisternal or sternopleural 

 suture, as. 



In many of the Nematocera, such as the mycetophilid shown in 

 Fig. 6, B, the anepisternum is divided, by a more or less vertical cleft, 

 into an anterior and posterior anepisternum, aae and pae. In the 

 culicids (Fig. 6, D), the dividing cleft extends as an oblique slash, 

 which cuts off the anterior anepisternum, aae, which becomes stranded 

 upon the prothorax (forming the so-called postspiracular area), Avhile 

 the posterior anepisternum, jjae, remains united with the rest of the 

 episternum, es, below it, and the suture between them becomes oblit- 

 erated. In the muscoid Diptera (Fig. 6, C), the anterior anepister- 

 num becomes greatly enlarged, and occupies most of the anepisternal 

 region, while the posterior anepisternum is greatly reduced, and is 

 rather closel}^ associated with the upper region of the epimeron, aein. 

 In the hippoboscid shown in Fig. G, F, the anterior anepisternum 

 merges with the rest of the episternum below it, when the suture be- 

 tween them becomes obliterated, and it is separated by a vertical cleft 

 from the posterior anepisternum, which becomes closely associated 

 with the up23er region of the epimeron, aem. In the sheep tick shown 

 in Fig, 6,F, these unions have become still more intimate, and the 

 cleft Avhich apparently divides the episternum, es, from the epimeron, 

 em, is in reality the anepisternal cleft, dividing the anterior anepister- 

 num (which unites with the rest of the episternum) from the posterior 

 anepisternum (which unites with the epimeron). The region in front: 

 of the cleft likewise unites with the notum above, and with the pro 

 thorax anteriorly, forming supporting arches above the front and 



I 



