DIPTERA 



783 



the presutural depression. (Fig. 

 looi, np.). 



The mesopleura. — The upper 

 part of the episterna (anepis- 

 terna) of the mesothorax (Fig. 

 looi r:es.). 



The s'ernopleura. — The lower 

 part of the episterna (katepi- 

 sterna) of the mesothorax (Fig. 

 lOOI, s'.). 



The pteropleura. — The upper 

 part of the epimera (anepimera) 

 of the mesothorax, (Fig. looi, 

 Pt.). 



The hypopleura. — The lower 

 part of the epimera (katepimera) 

 of the mesothorax (Fig. looi, 

 hy.). 



The metapleura. — The pleixra 

 of the metathorax. 



OTHER TERMS FOR PARTS 

 OF THE THORAX 



Fig. looi. — Diagram of the thorax of a fly 

 illustrating the terms applied by writers on 

 chffitotaxy to the areas of the thorax. The 

 positions of the more important bristles 

 are indicated by dots: ex, ex, ex, coxce; h. 

 c, humeral callus; h, halter; hy, hypo- 

 pleui'a; mes, mesopleura; np, notopleura 

 or presutural depression; po. e, postalar 

 callus; pr, propleura; pt, pteropleura; s, 

 scutellum; sq, sq, squamae or calypteres; 

 st,_ sternopleura; w. b. wing-base. (After 

 Riley and Johannsen.) 



The alar frenum. — ^A little 

 ligament dividing the supraalar 

 cavity into an anterior and a 

 posterior part. 



The humeral callus. — Each of 

 the anterior lateral angles of the 

 prescutum of the mesothorax, 

 usually a more or less rounded 

 tubercle. (Fig. looi, h. e.). 



The prealar callus. — A not 

 very prominent projection, situ- 

 ated before the root of the wing, on each side of the mesonotum, just back of the 

 outer end of the transverse suture. 



The postalar callus. — A more or less distinct rounded swelling on each side, 

 situated between the root of the wing and the scutellum. (Fig. lOoi, ^o. c). 



The presutural depression. — A depression, usually triangular in shape, at the 

 outer end of the transverse suture, near the notopleural suture (Fig. lOOi, np). 



The supraalar groove or cavity. — A groove on the mesothorax immediately 

 above the root of the wing. 



The scutcllar bridge. — A small ridge on either side of the scutellum connecting 

 it with the scutum, crossing the intervening suture. 



THE THORACIC BRISTLES 



The acrostichal bristles. — Two rows of bristles, one on each side of the mediaii 

 line of the mesonotum, the two rows nearest to the median line (Fig. 1002, a). 

 Those in front of the transverse suture are termed the anterior acrostichals or 

 preacroslichals ; those behind this suture, the posterior acrostichals or pos'acrosti- 

 chals. 



The anterior acrostichals. — See the acrostichal bristles. 



The discal scutellar bristles. — See the scutellar bristles. 



The dorsocentral bristles. — A row of bristles on each side next to and parallel 

 with the acrostichals bristles (Fig. 1002, dc). Those before the transverse suture 

 are termed the anterior, those behind, the posterior, or postsutural dorsocentrals. 



The humeral bristles. — One or more bristles inserted on the humeral callus. 

 (Fig. 1002, // m). 



