510 C. E. Osten-Sacken's essay on 



between the scutellar bridges. A bristle usually existing 

 immediately outside of the scutellar bridge, almost in a 

 line with the prsescutellar bristles, belongs to the dorso- 

 alar region, and has been already mentioned above as 

 the hindmost bristle of the supra-alar group. In the 

 Asilidce there are often two longitudinal short rows of 

 small bristles in front of the scutellum ; they may be 

 called prcescutellar roivs. 



C. Thoracic Pleural Bristles. 



Prothoracic bristle (Loew, Monogr. N. Am. Dipt., iii., 

 p. 33). — A strong bristle immediately above the front 

 coxfe, which exists in Loew's division Ortalina. The 

 bristle called Borste iihcr der VordcrJiiifte in Loew's paper 

 on HelomyzidcB, p. 16, is homologous to this. It also 

 exists in Cordylura, but not in Scatophaga ; in the 

 Calyptrata several bristles are generally found here. 



Mesopleural bristles. — Inserted on the mesopleura, in 

 the angle formed by the horizontal dorsopleural suture 

 and the vertical mesopleural suture. There are often 

 (for instance, in the section Oii(ditia) several bristles 

 here, arranged in a row along the vertical mesopleural 

 suture ; there are two such bristles in Scatophaga, none 

 in Dryomyza nor in Helomyza. In the Diptera Calyptrata 

 these bristles form a conspicuous row. 



Sternop)leural bristles. — One or several on the sterno- 

 pleura, below the longitudinal sternopleural suture. In 

 Loew's divisions Ortalina and Cephalina there is one 

 such bristle above the middle coxae. Loew calls it the 

 mesothoracie bristle, which name I cannot adopt, how- 

 ever, as it is too indefinite. There is one such bristle in 

 Seatuphaga, one or two in Helomyza and Blepharoptera , 

 two in Sapromyza, and three in Dryomyza ; none in 

 Loew's Flaty stamina. In some Anthomyice I perceive 

 three (one anterior, two posterior) ; in some Dexia and 

 Tachince also three (two anterior, one posterior) ; in 

 Sarcophaga three (one anterior, one posterior, and one 

 between them). 



Pteropleural bristles. — Inserted on the pteropleura ; 

 are of rare occurrence, and generally difficult to perceive ; 

 Tryp)eta, for instance, has a weak bristle inserted on 

 the pteropleura, under the root of the wing. 



Metapleural bristles. — On the metapleura ; they are 

 especially conspicuous in the Asilidce, where they form a 

 fan-like row. 



