NO. 13 



STAPH YLINIDAE BLACK WELDER 



69 



In Xantholinus (fig. 23 D) and Metopoucus there is a pair of large 

 triangular sclerites anterior to the sternum and lying free in the edge 

 of the anterior foramen. They occur in no other group and are said 

 to be present in only a few genera of the Xantholinini. 



The spiracles of the mesothorax normally lie in the intersegmental 

 membrane in the vicinity of the pronotal lobes. They usually lie in the 



2^. — Intrafamily variation in the form and structure of the 

 prosternal area (continued from fig. 22). 



A, Astcmis discopunctatus (Say). B, Pinofhilus parvipcnnis Csy. C, Lorinota 

 cingulata (Lee.). D, Xantholinus picipennis Lee. 



unsclerotized membrane as in Lithocharis (fig. 22 B) and Trigonurus 

 (fig. 22 D), but are incorporated into the posterior lobe of the pro- 

 sternum in Pinophilus (fig. 23 B). In Aleochara (fig. 22 A) they are 

 surrounded by the small peritremes, while in Lorinota (fig. 23 C) these 

 sclerites are so large as completely to close the coxal cavities behind. 

 The shape of the elytron is almost as individual as that of the 

 pronotum (fig. 24). It is impossible to classify these organs by form, 



