NO. 1687. THE THORAX OF IXSECT^—SyODGRA^S. 533 



there are but indistinct traces of tlie V ridge. The apex of the latter 

 is entirely lacking, so that the area corresponding with the median 

 part of tlie scutelhim of the Diptera or Lepidoptera here appears as 

 a median posterior lobe of the scntal region. This is very suggestive 

 of the Acridiidu'. The pseudonotum (/*^V) is a large plate equally 

 developed in both meso- and metathorax of adults, though conspicu- 

 ously absent in the nymphs. 



The simple type of tergum occurring in the Orthoptera has already 

 been described and is illustrated by Blatella (38, 40) and by GryJhis 

 (40, 50). Both of these forms present a meso- and metanotum of 

 almost typical diagrammatic form. The pseudonotum is lacking in 

 all Orthoptera (see p. ooS), and the divisions of the notuni are only 

 such as are indicated by the Ventral ridges. All other regional diversi- 

 fications are purely topographical. 



In a winged Locustid, Mhrocentrum, laurifoUum, neither the meso- 

 notum (3D) nor the metanotum (41) shows any subdivisions except 

 such as are marked out by elevations and depressions. Only rudi- 

 ments of the V ridge occur (F). A small-winged adult Locustid, 

 such as Anahriis simplex^ has the notum (42) of almost nymphal 

 simplicity. 



In the Acridiida^ the meso- and metanotum are almost identical 

 with each other. An under view of the mesonotum of liipiyiseus 

 phocnieopteriis (54) shows considerable departure from the other 

 Orthopteran families. The V-shaped ridge (T^) is low and flat and 

 not ridge-like. The posterior notal ridge {PNR) is, however, w^ell 

 developed and is almost phragma-like. Diverging forward and out- 

 w^ard from its middle are two high thin ridges (s, s) which do not 

 occur in the other families. The posterior reduplication {Rd) forms 

 a marginal thickening carrying laterally the axillary cords {AxC). 

 On the dorsal surface (53) five regions are distinguishable. The 

 first is a narrow median anterior area separated by a suture-like line 

 {ani') formed by the anterior notal ridge. The second occupies 

 most of the back and consists of two large anterior lateral lobes and 

 of a smaller median posterior lobe. It bears the anterior notal wing 

 processes {ANP). The third and fourth divisions lie laterad of the 

 median posterior lobe and are demarked by the lines of the posterior 

 notal ridge (pnr) and the ridges {s, s) diverging from the latter. 

 Each is a transverse, elongate oval area tapering mesially, laterally 

 bearing the posterior wing process (PNP). The fifth region, marlced 

 in front by the line of the posterior notal lidge {pnr)^ is the thick- 

 ened posterior reduplication carrying the axillary cords {AxC). 



This description, as far as the writer can see, expresses the facts 

 concerning the Acridiid mesonotum. Yet, various entomologists, by 

 a vigorous exercise of the imagination, have made out four transverse 

 divisions, thus compelling the locust to fall in line with the beetles, 



