1918] Crampton — Study of Terga and Wing Bases 9 



which has been retained in the Dermaptera, but has become lost, 

 or was never developed, in the Coleoptera. A suggestion of this 

 fold is also retained in the Plecoptera, as is shown in the posterior 

 tergal fold designated as "pt" in the metathoracic region of the 

 Plecopteron depicted in Fig. 1. There is a tendency for this region 

 to become reduced, or to unite with the surface which it overlaps, 

 so that the narrow continuation of the surface of this fold toward 

 the point designated as "x" in the metathorax of Fig. 4, may 

 possibly be homologous with the similar narrow continuation of 

 the region beside the postscutellum, toward the point labeled "x" 

 in Fig. 2 (at the base of the sclerite "sa"). 



In the foregoing descriptions, I have laid especial emphasis upon 

 the resemblance between the Coleoptera and Dermaptera, as illus- 

 trated by the preponderance in size of the metathorax over the 

 mesothorax; the relative width, and the outlines of the nota; the 

 triangular shape of the mesonotum, and its overlapping the meta- 

 notum, with the consequent reduction of the mesothoracic post- 

 scutellum; the development of ridges in the metanotum for holding 

 the elytra in place; the formation of a transscutal suture; the 

 retention of the myodisc rather than of the tegula in the metanotal 

 region; the outline and extent of the pteralia, etc. Similarly, the 

 marked resemblance between the Embiids and Plecoptera is shown 

 in the relative size of the nota, the width and the outlines of the 

 nota; the location of the prescutum in front of the anterior margin 

 of the wing-base; the development of the mesothoracic postscutel- 

 lum; the development of the tegulae in both segments; the elon- 

 gate notopterale, etc. On the other hand, in emphasizing these 

 similarities between the Coleoptera and Dermaptera. or between 

 the Embiids and Plecoptera, one should not lose sight of the fact 

 that the Coleoptera and Dermaptera are both related to the Em- 

 biids and Plecoptera, although the Dermaptera, being the more 

 primitive of the two, are nearer to the Embiids and Plecoptera 

 than the Coleoptera are. 



The cerci of certain larval Coleoptera, such as Galerita janus, 

 and of certain Dermaptera such as Diplatys severa (in which 

 segmented cerci precede the forceps of the adult forms) are very 

 similar, even when the individual segments are compared together, 

 and the cerci of both groups resemble those of the Plecoptera 

 extremely closely, so that the evidence of the cerci would point to 



