2 PROCEEDESTGS OF THE NATIONAL MUSEUM vol. no 



the aedeagus indicates that spretus is a distinct species. Any further 

 evidence bearing on this opinion naturally is very desirable. 



It is chiefly on the basis of the differences in the aedeagus that 

 mexicanus has been found to be distinct from the species commonly 

 misidentified as M. mexicanus by American entomologists. The 

 species most frequently misidentified as mexicanus is M. hilituratus 

 (Walker), and the structure of the aedeagus further suggests that 

 three subspecies merit recognition. 



Limits of Group 



The mexicanus group consists of Melanoplus mexicanus and five 

 closely related species. There are five subspecies in addition to the 

 typical ones. Distribution is limited to North America, from southern 

 Mexico to the Arctic. At this stage in our knowledge of the species 

 groups of Melanoplus, the best that can be offered as a definition of 

 the mexicanus group is a somewhat loose combination of the following 

 characters : 



1. Pronotum with hind margin of the dorsal surface produced posteriorly, 

 either broadly angulate or rounded (fig. 15). 



2. Tegmina usually covering most or all of abdomen, often extending beyond 

 it, sometimes covering only about a third of the abdomen (pi. 5), but always 

 elongate, never lobate. 



3. Male cercus (figs. 7, 8) varying from slender and somewhat rectangular to 

 broadly and irregularly oval. 



4. Male subgenital plate tending to develop a dorsal lip at the apex, sometimes 

 posteriorly produced, frequently with twin apical knobs (figs. 11, 16). 



5. Dorsal valve of aedeagus anterior to the apical portion of the main stem, 

 usually well sclerotized, more or less concave laterally (figs. 1, 2, 3). Ventral 

 valve of aedeagus relatively short, straplike, its apex usually visible in lateral 

 view near the base of the dorsal valve, dorsad of the accessory lobe. Accessory 

 lobe of aedeagus moderate to large, weakly sclerotized. 



The name of the mexicanus group is taken from the specific name 

 that has been used most often in the literature in recent years, though, 

 as now restricted, mexicanus is neither the most widely distributed 

 nor the most important species. M. hilituratus is the most widely 

 distributed, and since the outbreak of spretus ended it has been the 

 most important. Hebard (1935a, p. 57) recognized a borealis group; 

 earlier (1928) he briefly discussed some members of the mexicanus 

 group as he conceived it. It seems to us that the mexicanus group is 

 sufficiently cohesive to be recognized as we are treating it, with 

 borealis included, at least imtil the group relationships within Melano- 

 plus are better understood. M. Jemur-rubrum (De Geer), genotype 

 of Melanoplus, has not been included in this group, though the male 

 cercus is very much like that of borealis borealis. The subgenital 

 plate oi jemur-rubrum is not produced apically as in the members of 

 this group. A distinctive character of jemur-rubrum is a small 



