188 



Annals Entomological Society of America [Vol. X, 



insects. It is at once apparent from a glance at Fig. 1, that the 

 two ventral prothoracic intersegmental plates designated as 

 " ps'' in intersegmental region I (i. e. "Int. I") are in every way 

 homologous with the two ventral metathoracic intersegmental 

 plates designated as "^5" in intersegmental region V (i. e. 

 "Int. V"). In the Plecopteron Capnia (Fig. 1) there are two 

 ventral prothoracic intersegmental plates "^5" in interseg- 

 mental region I, but in the closely related Plecopteron Leuctra 

 (Fig. 3) the anterior one of the two ventral prothoracic inter- 

 segmental plates "/?5" has almost disappeared in region I, while 



Fig. 1. Lateral and ventral region of the prothorax of Capnia, the mesothorax of 

 Eosentomon, and the metathorax of Japyx drawn as though spread out in 

 one plane. Based, in part, upon figures by Prell, 1913, and Verhoeflf, 

 1904. 



Fig. 2. Head of an embryo of Eutermes, stage "F," taken from Fig. 28, Plate 3, 

 of paper by Holmgren, 1909. (Figure slightly modified). 



Fig. 3. Lateral and ventral regions of prothorax of Leuctra, drawn as though 

 spread out in one plane. 



Fig. 4. Dorsal view of prothorax and mesothorax of Japyx, based on figures from 

 various sources. 



