38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



Scutum.. — The largest plate of the metanotum is the scutum ex- 

 tending backward from the anterior membrane (b). The limitation 

 between the scutum and the scutellum, the scuto-scutellar suture, is 

 visible as a ventrally elevated ridge which becomes indistinct laterally. 

 The anterior apodeme divides the scutum in two subdivisions, the 

 scutum proper and the scutular lobes. The latter extend beyond the 

 posterior prealar process of the prescutum as was stated above and 

 cover the process dorsally. Externally the scutum is one continuous 

 lialf spherical plate medially divided by the scutular groove. In- 

 ternally projections of the scutellum extend far into the scutum. From 

 the inner externo-lateral corners of the scutum proper arise two pairs 

 of parapsidal ridges (k) which converge in a slightly curved line 

 medially. 



Scutellum. — The scutellum, which is posteriorly limited by a mem- 

 brane (a), encloses the scutum in a half circle. The scuto-scutellar 

 suture is produced anteriorly forming the lateral limitations of the 

 scutellar groove. It extends to the anterior margin of the scutum. 

 The space between the produced suture is strongly depressed ex- 

 ternally forming a wide scutellar groove. The posterior end of the 

 mesoscutellum rests in this groove. From the posterior lateral corners 

 of the scutellum arise two armlike formations which converge an- 

 teriorly meeting at about the middle of the scutum. These forma- 

 tions correspond to the endodorsum (Amans), V-shaped ridge (Snod- 

 grass), or median apodeme (Hopkins). Where they join they are 

 connected with the scutellar groove. It is likely that the intensive 

 study of the endodorsum of the Scolytidae will bring out many new 

 features for the systematic arrangement of this group. 



Postnotuni. — The postnotum or pseudonotum is subdivided into 

 three transverse divisions, the precosta (Pc), with the prominent 

 prealar bridges (1) and the postphragma (Pph). The precosta is a 

 simple band separated from the postphragma by the postnotal apodeme. 

 Laterally it is produced into prominent prealar bridges. The inner 

 margin is developed as a heavily chitinized ridge which is posteriorly 

 divided, forming a ring and externally produced into a slender hook, 

 the prealar hook (m). 



The postphragma is a slightly ventrally bended band. The post- 

 notum is visible externally, giving the appearance of a reduced tergum 

 at the first abdominal segment. 



Metapleura. — The pleuron of the metathorax (fig. 17) consists 

 chiefly of two plates, the episternum (fig. 17, Eps) and the epimeron 

 (Epm). The pleural suture (Ps) is externally represented as a dis- 

 tinct line, internally as a ridgelike structure. From the pleural suture 



