98 ENTOMOLOGICAL SOCIETY 



ter only and is developed in the membrane back of the true 

 notum. Verhoeff has given the name of pseudonotnm to this 

 plate in the Euplexoptera (Dermaptera) and this is probably 

 as good a name as can be suggested. It is well shown in 

 figures i8, 24, and 25, Pn. In the Coleoptera the pseudonotum 

 carries the posterior phragma. 



The presence of the pseudonotum in the euplexopteran 

 metathorax (fig. 18, Pn) is one of the principal points in the 

 present discussion, for the pseudonotum of the metathorax is 

 a prominent Coleopteran character (figs. 24, 25, Pn), but one 

 that does not occur in the Orthoptera. It is absent in the meso- 

 thorax of both the Euplexoptera and the Coleoptera, unless 

 in the latter the small sclerites (fig. 19, ^) uniting the meso- 

 notum to the metanotum are its representatives. 



The sclerite in beetles here homologized with the pseudo- 

 notum of the Euplexoptera is the " tergum " of Straus-Durck- 

 heim, the " postscutellum " of Audouin and authors following 

 him, and the " acrotergite " of the first abdominal segment as 

 interpreted by Berlese. 



The thoracic pleura are in each segment made up of several 

 plates and, although they vary considerably in different orders, 

 yet one fundamental plan is always evident. This plan is well 

 illustrated by the mesopleurum of Spodromantis guttata (Man- 

 tidse) (figs. 2 and 4), but the same structure is easily recog- 

 nized in the other examples given, viz., the mesopleurum of 

 Ischnoptera hyalina (Blattidae) (fig. 3) ; the propleurum (fig. 

 8) and the mesopleurum (fig. 5) oi Byrsotria fumigata (Blat- 

 tidae) ; the propleurum (fig. 10), the mesopleurum (fig. 9), 

 and the metapleurum (figs. 11 and 12) of Spongophora apici- 

 dentata (Forficulidae) ; the mesopleurum (figs. 16 and 17) and 

 the metapleurum (figs. 20 and 22) of Cyllene robinice (Ceram- 

 bycidse), and the mesopleurum (figs. 21 and 23) and the meta- 

 pleurum (figs. 26 and 27) of Calosonia scrutator (Carabidse). 



A typical pleurum, then, is constructed as follows : A thick 

 internal vertical, oblique or horizontal ridge (PR) extends 

 from the base of the coxa to the base of the wing. This is 

 the pleural ridge. It is formed by the approximated, infolded, 

 and united edges of two plates, one, the epimertwi (Epm), 

 lying above or behind the ridge and the other, the episternum 

 (Eps), lying below or before it. The external pleural suture 

 (PS) between these two plates of course marks the position 

 of the internal ridge. The upper end of the pleural ridge pro- 

 jects as an arm supporting the costal head of the wing and is the 

 wing process (WP) or alar apophysis. The lower end of the 

 ridge nearly always projects as an arm, the coxal process 



