360 Annals Entomological Society of America [Vol. XI, 



could be brought about. At any rate, the mesosternum appears 

 to be dovetailed into the metasternum and the first abdominal 

 sternum appears to be dovetailed into the metasternum, which 

 is a condition peculiar to the grasshopper group (so far as I am 

 aware). None of the crickets or katydids which I have exam- 

 ined has a mesothoracic ring "pc2" about the base of the coxa 

 (Figs. 1 and 2), or a metathoracic sclerite like those shown in 

 Fig. 2, "acs" and "st," so that these structures, together with 

 the "dovetailed" condition of the sternal regions, may be 

 characteristic of the grasshoppers alone, and serves to further 

 separate them from the crickets and katydids. 



OTHER INTERPRETATIONS. 



The Tergal Region. 



Brooks, 1882, page 247 (also Fig. 130 of "Acridium'') is 

 apparently responsible for the frequently repeated statement 

 that the pronotum of the grasshopper is divided into four 

 regions homologous with the prescutum, scutum, scutellum, 

 and postscutellum of the other segments of the thorax, and this 

 view has been adopted by Comstock and Kellogg, 1902 (p. 21) 

 and many other writers. The fact that this view cannot be 

 the correct one, however, is demonstrated by the occurrence of 

 five or even six such areas in the pronota of some grasshoppers, 

 as well as by the fact that the four principal tergal subdivisions 

 never occur as transverse bands in the other segments. The 

 line of division between the true scutum and scutellum never 

 lies directly over the pleural suture (as is supposed to be the 

 case in the pronotum), since the true scutellum is usually tri- 

 angular in outline. Furthermore, the true postscutellum is 

 always formed as a plate distinct from the plate in which the 

 prescutum, scutum, and scutellum are demarked, and, in con- 

 nection with many other facts such as the nature of the mus- 

 culature attached to the regions in question, etc., the pronotal 

 subdivisions cannot possibly be interpreted as representing the 

 four typical tergal subdivisions, but evidently owe their origin 

 to mechanical causes as pointed out in the preceding discussion. 



Brooks, 1882, (p. 250, and Fig. 133) would interpret the 

 narrow transverse marginal region of the mesonotum ("pt2" of 

 Fig. 3 of this paper) as the "prescutum," but it is clearly not 

 the entire prescutum, being merely the narrow anterior mar- 



