12 PROCEEDINGS OF THE NATIONAL MUSEUM voi,. no 



in Guerrero at altitudes ranging from 5,000 to 8,000 feet, and in 

 Michoacdn from 6,000 to 8,000 feet. The series of about 35 Mexican 

 specimens examined includes captures made in all months except 

 January and April, and it is evident that there is more than one 

 generation, perhaps continuous breeding, slowed down by unfavorable 

 local conditions. 



Melanoplus bilituratus (Walker) 



This widespread, variable species is represented by most of the 

 material which, in recent years, has been referred to Melanoplus 

 mexicanus mexicanus. Exceptions are specimens now recognized 

 as true M. mexicanus, and M. spretus. Specimens of M. 

 bilituratus from the Far West occasionally have been confused with 

 M. devastator, sometimes referred to as M. mexicanus devastator. As 

 mapped by Newton and Gurney (1956-57) (as mexicanus complex), 

 bilituratus occurs almost throughout the United States, except for 

 peninsular Florida. Our present maps (figs. 5, 6) are based on males 

 the aedeagi of which have been examined to determine the subspecies 

 concerned. 



WhUe more detailed research may warrant the recognition of a larger 

 number, the material now examined, which is representative of most 

 areas, seems to justify only three subspecies. There is some indication 

 that ecological subspecies, recognized by color and size, do occur, 

 especially in Canada and Alaska (see p. 20). Brooks (1958, p. 20) 

 has recognized these differences by treating atlanis (RUey) as a valid 

 subspecies; however, the senior author doubts the value of applying 

 names to these questionable ecological subspecies at this stage in the 

 study, and atlanis is regarded as a synonym. 



The reason that the three populations concerned are recognized 

 as subspecies, and not species, is that in each case intergradation in 

 structural characters of the aedeagus occurs. Except for material 

 from Texas, intergrading specimens are here discussed under the 

 appropriate subspecies. Those from Texas are of sufficiently un- 

 certain relationship that it seems best to discuss them in one place. 

 Males from Gainesville and several other Texas localities as listed 

 below are typical or essentially typical of bilituratus vulturnus. Some 

 divergence, in that the carina of the dorsal valve of aedeagus is not 

 well developed, is shown by some specimens from Austin and Wichita 

 Falls. The male from Phantom Lake, Davis Mountains, appears 

 typical of bilituratus defectus, but one from nearby Marfa and those 

 from Blanco County, Plainview, Lubbock, and Sweetwater are not 

 typical bilituratus defectus and are best considered intermediates of 

 uncertain relationship. The specimen from Kokernot Mountain, 

 Alpine, Tex., is unusual in that the anterior margin of the dorsal 



