SMITHSONIAN INITSCKLLANEOUS COLLECTIONS 



\OL. 94 



ill narrow laterotergal sclerites (E, Itg). The spiracles of the eighth 

 segment He in the lower parts of the tergum of this segment (fig. 

 19 A). The median sternal plates of segments // to VI or F// are 

 flanked by narrow laterosternites (fig. 2 E, 1st) and the sterna overlap 

 the edges of the terga, the laterosternites being inflected. In Tridacty- 

 lus and Rhipipteryx a small internal vesicle opens by an external pore 

 (E, 3;) on the laterosternite of the third segment. According to Car- 

 pentier (personal communication) a similar anterior vesicle opens on 

 the laterosternite of the second segment in Rhipipteryx carhonaria. 

 The terminal segments of the tridactylid abdomen have many peculiar 

 features, as will be shown in the description of the genital organs ; but 



atg' acs AN 



2Ph 



Fig. 3. — Relation of the phragmata to the segmental plates of the dorsum. 

 Dtssosteira Carolina. 



A, vertical section of dorsum of metathorax just to right of median plane, 

 showing the antecostal sutures {acs) and phragmata {sPh, sPh) marking the 

 true intersegmental lines ; the dorsum is occupied by a wing-bearing plate, the 

 alinotum {AN.%), and a postalar postnotum (PNs) equivalent to the acrotergite 

 (atg) of the alinotum. B, posterior view of the first abdominal tergum, the 

 lobes of the third phragma, and the right tympanal capsule. 



the well-developed ovipositor of Rhipipteryx (fig. 19 A, Ovp) is 

 surprisingly similar to the ovipositor of Tetrigidae and Acrididae. 

 The male organs, on the other hand, have no resemblance whatever 

 to those of Acrididae or to those of Tetrigidae. 



The abdominal terga of the Acrididae, except the tergum of the 

 first segment, are siinple plates with no sutural divisions (fig. i). 

 The dorsal muscles arise on each tergum some distance behind the 

 anterior margin (fig. 10 A), and the line of attachment here is marked, 

 particularly in the male, by a short secondary tergal ridge (tr) on 

 each side. True antecostae appear to be absent, since the muscles are 

 inserted posteriorly on the weak anterior margins of the tergal plates. 

 In the Tetrigidae, on the other hand, each tergum has a distinct margi- 

 nal antecosta. Tergal apodemes are absent, except in the ninth segment, 

 where, as in Dissostcira (fig. 14), there may be a pair of apodemal 



