8 Psyche [February 



region of the tergum called the suralare (Crampton, 1914-1916) 

 and serves as one of the pivots for the wing in the movements of 

 flight, although it may become detached from the remainder of the 

 tergum in a few rare instances, as Pantel considers to be the case 

 in the Dermaptera. The posterior wing process "a" of the meso- 

 thorax is very similar in both Coleoptera and Dermaptera (Figs. 2 

 and 4), being rather long and slender in these insects, while it is 

 shorter and more blunt when it occurs in other members of the 

 group (Fig. 1, "a"). The basanal pterale "sa" is proportionately 

 much larger in the metathorax of the Coleoptera and Dermaptera 

 (Figs. 2 and 4) than in the Plecoptera and Embiids (Figs. 1 and 3). 



In both the Coleoptera and Dermaptera (Figs. 2 and 4) there is 

 a pronounced tendency for the tergal region of the wing bearing 

 segments to become broader than long, and, with the Strepsiptera, 

 and certain Orthoptera, these insects comprise the few forms in 

 which the metathorax surpasses the mesothorax in size. Unlike 

 the Plecoptera and Embiids, there is a well marked tendency in 

 the Coleoptera and Dermaptera (Figs. 2 and 4) for the mesonotum 

 to take on a triangular outline, and for the scutellar region of the 

 mesonotum to become pointed posteriorly and to overlap the an- 

 terior portion of the metanotum behind it. Correlated with this 

 tendency for the scutellum of the mesonotum to overlap the meta- 

 notum in the Coleoptera and Dermaptera, there is a well marked 

 tendency toward the reduction of the mesothoracic postscutellum, 

 which is well developed in the Embiids and Plecoptera. 



In the metathorax of Coleoptera and Dermaptera (Figs. 2 and 

 4) two alar ridges or "alacristae" labeled "ac" serve to hold the 

 elytra in place when at rest, and in many Dermaptera, they are 

 provided with bristles which doubtless aid in holding the elytra in 

 position. In both Coleoptera and Dermaptera, the metathoracic 

 scutum is traversed by a "transscutal suture" ("tr" of Figs. 2 and 

 4). which is apparently absent in most of the other members of this 

 superorder; and it is at once apparent from the study of the tergal 

 region and the wing bases, that the Coleoptera are very similar to 

 the Dermaptera in regard to these features, while the Embiids are 

 very similar to the Plecoptera in the character of their tergal regions 

 and wing bases. 



The presence of the posttergal fold "pt" of Fig. 4 is a "Pandic- 

 tyopterous" character (well developed in Isoptera, Mantids, etc.) 



