48 NORTH AMERICAN DIPTERA. 



central and acrostichal are represented by the hindmost 

 bristles forming a prescutellar row in front of the scutel- 

 lum. 



Scutellar, bristles along the margin of the scutellum, 

 which may be distinguished from the Dorsoscutellar. 



PLEURAL BRISTLES. 



Propleural, a bristle or bristles inserted on the lower 

 part of the propleura, immediately above the front coxa. 



Mesopleural, bristles inserted on the mesopleura, near 

 the angle formed by the dorsopleural and mesopleural 

 sutures. 



Sternopleurdl, one or several bristles below the sterno- 

 pleural suture; mesothoracic of Loew. 



Pteropleural, bristles inserted on the pteropleura, rarely 

 present and difficult to distinguish. 



Metapleural, bristles inserted on the metapleura, es- 

 pecially conspicuous in the Asilidae, and named by 

 Lynch the 



Trichostical bristles, a fan-like row on the metapleura, 

 conspicuous in some families. 



Hypopleural bristles, a row or tuft of usually small bris- 

 tles on the hypopleura, occurring in the Tachinidae, 

 Dexiidae, Sarcophagidae, and a part of the Muscidae, first 

 recognized by Osten Sacken. 



ABDOMINAL BRISTLES. 



Marginal bristles, bristles inserted on the posterior 

 margins of the segments above, especially conspicuous 

 in many Tachinidae. 



Discal bristles, usually one or more pairs inserted near 

 the middle of the segments before the hind margins. 



Lateral bristles, one or more bristles situated on or 

 near the lateral margins of the segments. 



In addition, a number of terms are used to designate 

 the inclination of the bristles, often important in describ- 

 ing the cephalic bristles. The more important of these 



