1917.] NATURAL SCIENCES OF PHILADELPHIA. 267 



these species are of a closely similar type antl do not afford the 

 striking differential features usually found in the species of the genus 

 Melanoplus. 



Type: cf ; Copete Mine, thirty miles east of Carbo, Sonora, Mexico. 

 (F. C. Nicholas.) [American Museum of Natural History.] 



Size largest of the forms of the Aridus Group; form moderately 

 robust, distinctly heavier than in typical desultorius. Interocular 

 space slightly narrower than first antennal joint. Vertex and frontal 

 costa as in aridus and desultorius. Eyes distinctly longer than 

 infra-ocular portion of gense. Pronotum much as in desidtorius; 

 disk gently arched transversely and longitudinally, the lateral 

 margins rounded; median carina distinct on cephalic half of prozona 

 and on metazona, obsolete on caudal half of prozona; transverse 

 sulci well developed, the first failing by a very brief space to break 

 the median carina, the other two complete, cutting the mecUan line; 

 caudal margin of pronotum rotundato-obtuse-angulate. Prosternal 

 spine moderately elongate, rounding sharply distad to the acute 

 apex. Interspace between mesosternal lobes slightly more than 

 twice as long as least width; metasternal lobes contiguous. Tegmina 

 broad ovate, decidedly overlapping, with caudal margin truncate and 

 showing a broad but weak concavity toward the apex of the humeral 

 trunk. The small, slightly divergent furcula, triangular and but 

 little specialized supra-anal plate and elongate, very slender, mod- 

 erately incurved cerci are much as in desultorius. The subgenital 

 plate' is broader than in that species, much broader than in aridus, 

 with distal margin Ijroadly rounded. Other features are found to be 

 as described for desidtorius.^^ 



Allotype: 9 ; same data as type. [American Museum of Natural 

 History.] 



Agrees with male except in the following 



features. Size much larger, form more 



robust. Interocular space slightly wider 



than first antennal joint. Pronotum with 



median carina percurrent, strongest on 



metazona, similarly cut by the transverse 



sulci. Interspace between mesosternal 



lobes with width contained in length Fig. 5.— Melanoplus desultorius 



about one and one-half times, that i^'T'^' ^;^. subspecies. 



' (Jutline 01 lemale tegmen. 



between metasternal lobes very narrow. Allotype. (X 3.) 



18 By Rehn, Proc. Acad. Nat. Sci. Fhila., 1907, p. 51, (1907). 

 19 



