556 PROCEEDINGS^ OF THE NATIONAL MVf^EVM. vol. xxxvi. 



{PS) separating the episterniini and epimerum externally, and a 

 pleural ridge internally. In (rrylhis {M\) the parts are highly modi- 

 fied, but all are represented. The })leural ridge develops a large 

 scapula-like internal i^late (/M) lying within the notuni. In Aitahnis 

 the preepisternuni is not a distinct jilate. It is when the Acridiidre 

 are reached, liowever, that the greatest modification is found. Here 

 the pronotum (51) extends downward on the side to the base of the 

 leg reducing the epistermnn {I'J }>><) to a small plate in front of the 

 coxa, and the epimerum {Epm) to a small plate behind the coxal 

 articulation and fused to tlie notal rim. A rudimentary trochantin 

 {Tn) is also present. 



In thus usurping the territory of the })leurum the jn'onotum has 

 also taken over the function of the former and has become modified 

 accordingly. An inner view {7)-l) shoAvs a prominent pseudoi)leural 

 notal ridge {NR) bearing an arm (A^i) near its loAver end, just as 

 does a normal pleural ridge (see 44-, 55), and terminating below in 

 a psendoplenral coxal process {NCxP) to which the coxa is articu- 

 lated. A large posterior reduplication {Rd) back of the posterior 

 groove and ridge (51, 52, ?:) overlajjs a large ])art of the mesothorax. 



The Acrid i id pronotum is thus highly specialized, doing duty as 

 both notum and pleurum, and its subdivision into four transverse 

 parts can not reasonably be cited as a tyjiical examj)le of the quad- 

 ruple structure of the insect tergum. Yet it is invariably used to 

 illustrate the jn'escutum, scutum, scutellum, and postscutellum. But 

 it is clearly illogical, as shown in another part of this paper, to offer 

 as " typical " an example that is confessedly not so! 



8. Meso- and metapleura closely resemble each other. In most 

 cases illustrations of either one will serve for both. 



Tn the]\Ianti(hr (27, 2S) the pleural suture (AS') is nearly horizontal, 

 but othei'wise the meso- and metapleurum is of the typical general- 

 ized form. (Comjiare 27, 28, with text figs. 3 and 4.) In Blattida- 

 {^Byraotrla fu))ii<i<it(i 82) the pleural parts are modified on account of 

 the flattened shape of the body, l)ut in a side view {hchnoptera 

 hyal'tna 35) the typical structure can be made out. The pleural 

 suture {PS) separates the small dorsal epimerum {Ejmi) from the 

 larger ventral episternum {Eps). An internal view (33) show^s a 

 pleural ridge {PR) and arm {PA) in normal relations to the other 

 parts. One preparapterum {P) is usually present, and below this an 

 indistinct jDreepi sternum (35, Peps) fused wnth the episternum 

 {Eps). At least it is evident that if a preepisternum is present it 

 must occupy some such position. Yet Verhoeff (1903) regards the 

 subdivision (eps) on the posterior edge of the episternum (Eps) as 

 the " katopleure," while the j^late he so designates in the Euplexoptera 

 lies before the episternum. This Euplexopteran sclerite (94, Peps), 

 then, is Verhoeff's " katopleure " or the preepisternum (Peps) of the 



