258 NEW NORTH AMERICAN MELANOPLI (ORTHOPTERA) 



A detailed discussion of the problems found in the genus Melan- 

 oplus will be given at a later date. For the present we would 

 remark only one vital error in Scudder's treatment. That au- 

 thor's efforts were concentrated in an attempt to find some valid 

 character to separate Melanoplus from Podisma. He determined 

 the fact that the typical species of Melanoplus had a narrow 

 mesosternal and metasternal interspace, while in typical species 

 of Podisma these intervals were wider. Further study showed 

 that this was not universal, but he considered it the most satis- 

 factory feature for the generic assignment of species, and sep- 

 arated Melanoplus from Podisma thereby in his key. 



After careful study of the situation, we have found that the 

 width of the mesosternal and metasternal interspaces is subject 

 to such individual variation that it is frequently of no diagnostic 

 value, even for specific separation. In addition, we note that 

 the forms of the Melanopli developed in a temperate environ- 

 ment have in the great majority of cases the mesosternal and 

 metasternal interspaces narrow, while those developed in an 

 arctic or arctic alpine environment have these interspaces usually 

 broad. As a result, we find that arctic or arctic alpine species 

 of Melanoplus have the mesosternal and metasternal interspaces 

 fully as broad as in the species of Podisma, the majority of the 

 species of which genus are found in arctic or arctic alpine regions. 

 We are unable to find a single diagnostic feature to separate 

 these genera. That Melanoplus and Podisma represent two 

 distinct units is clear. In each case the genus divides into numer- 

 ous sections, many of which are readily separable from the others 

 by distinctive features. In fact we again find a situation much 

 resembling that which occurs in the Tettigoniid genera Cono- 

 cephalus and Orchelimum, and of which Rehn and Hebard have 

 said, " Material of the two genera is easily separated by a decidedly 

 different general appearance, but when the characters of the two 

 are compared, the variation in each genus leaves us unable to 

 state a single absolute difference." 



As a result of Scudder's misconception of the significance of 

 the widening of the mesosternal and metasternal interspaces, 

 that author assigned to Podisma the following species, all of 

 which are clearly members of the genus Melanoplus: nubicola 

 Scudder, stupefacta Scudder, dodgei (Thomas), ascensor Scudder, 



