10 Psyche [February 



a " Plecopteroid " ancestry for the Coleoptera and Dermaptera. 

 The segments of the leg are very similar in Embiids, Plecoptera 

 and Dermaptera, and the relationship of the Dermaptera to the 

 Plecoptera is likewise shown by a comparison of the thoracic 

 sclerites (or of the head region) of a nymph of the Plecopteron 

 Perla with those of the Dermapteron Arixenia, the resemblance 

 being very striking, as has been shown in a paper dealing with the 

 thoracic sclerites of immature Pterygotan insects, which will soon 

 be published. The tendency toward the shortening and thickening 

 of the fore wings is quite marked in certain Plecoptera, and the 

 pleural thoracic sclerites of the Embiids are in many respects very 

 like those of the Dermaptera. In this connection, I would call 

 attention to the fact that in the Embiids (Fig. 3) the nature of the 

 postscutellar region of the metathorax and the first abdominal 

 segment, with the bulging lateral regioijs, is very suggestive of the 

 condition found in the Strepsiptera; but, since Dr. Pierce is mak- 

 ing a comparison of the thoracic region of the Strepsiptera with 

 other insects, which he finds more similar to the Strepsiptera than 

 the Embiids are, the affinities of the Strepsiptera can be more 

 accurately determined when the results of his extended studies 

 are published. 



Although the study of the terga and wing bases points to a close 

 relationship between the Dermaptera and Coleoptera, and between 

 the Embiids and Plecoptera, the evidence aflForded by these struc- 

 tures alone is insufficient to establish the affinities of the insects in 

 question. On this account, a comparative study of the strjictures 

 least subject to modification, and those situated in widely sepa- 

 rated parts of the body, has been undertaken in order to demon- 

 strate the relationships here proposed. Such an extensive treat- 

 ment of the subject, however, requires more space and plates than 

 can be afforded a single article; so that the summing up of the 

 arguments for the relationships here proposed, can be more con- 

 vincingly set forth after the evidence from the more extensive 

 study of the parts has been presented in the proposed series of 

 articles dealing with this subject. 



Bibliography. 



1914a. Crampton — Notes on the Thoracic Sclerites of Winged 

 Insects. Ent. News, 25, p. 15 — (Sclerites of Dermaptera 

 and Plecoptera figured) . 



