558 PROCEEDINGS OF THE NATIONAL MU;<!EUM. vol: xxxvi. 



bases form lines on the dorsal surface (53 -s) which mark off two oval 

 posterior lateral areas not represented in other families. 



If the four divisions of the notmii (38), as marked out b}^ the three 

 ventral ridges (40), are called the prescutum, scutum scutellum, and 

 postscutellum, it must be borne in mind that they are not homolo- 

 gous Avitli the divisions so named in the tergum of Lepicloptera, 

 Hymenoptera, and Diptera. The first division is a narrow marginal 

 strip carrAang the prephragma (Aph) when this is present. The 

 second is a large bilobed plate carrying both the notal wing processes 

 [AXP, PXP), the third consists of a triangular median area and 

 of two posterior lateral arms, the fourth is a posterior marginal band 

 consisting of the posterior reduplication (Ed) and terminating later- 

 ally in the axillarj^ cords (AxC). This last subdivision can in no 

 v\ay be identified with the "' postscutellum " of other orders, such as 

 Coleoptera — the representative of this plate is lacking in Orthoptera. 



5. Pseudonotum absent in both mesothorax and metathorax. 

 Posterior marginal part of notum, which some entomologists have 

 called '* postscutellum " in Orthoptera, not the homologue of this 

 plate in other orders. 



In many Orthoptera, especially the Acridiidu' (57), the first ab- 

 dominal tergum (IT) presents an anterior subdivision (If) whose 

 median dorsal part fuses with the metanotum, but whose lateral 

 parts are mostly free from the metathorax, and on each side enter 

 into the formation of an arm of the first abdominal tergum, extend- 

 ing downward before the auditory organ (.i^i;). Internally, on the 

 line betAveen these two subdivisions of the first abdominal tergum, 

 is a prominent ridge. In other Orthoptera this anterior subdivision 

 and the ridge are less developed, in some cases it amounts to only a 

 thinner anterior area Avhicli is ()verlap})ed by the reduplication of 

 the metanotum. 



This abdominal tergum could claim no place in the present discus- 

 sion were it not that many entomologists haA'e regarded its anterior 

 subdivision as a part of the thorax. Voss (1905), for example, has 

 identified it as the pseudonotum (postscutum, Voss) of the metathorax 

 and the internal ridge as the pgstphragnui. The part in question, hoAv- 

 BA^er, and the main plate of the first abdominal tergum (57, It and 77') 

 are unquestionably anatomically continuous. MoreoA'er, the first is 

 best developed in the Acridiidiie, Avhile in Blattidjo it is represented 

 only b}^ the Aveakly chitinized anterior half of the tergum oA^erlapped 

 by the metanotum, a subdivision such as all the abdominal terga 

 present. Berlese (1906) regards it as a part of the first abdominal ter- 

 gum, but he also thus identifies the pseudonotum (postscutellum) of 

 the metathorax in Coleoptera. The present Avriter, however, sees no 

 reason for regarding these parts in the tAVo orders as the same. Any- 

 one can see that they are not similar in appearance, and that their 



