90 NORTH AMERICAN ACRIDIDAE (oRTHOPTERa) 



Two genera, three species and one geographic race are included, 

 all occurring in the territory under consideration, though two of 

 the species find their northernmost hmit of distribution just over 

 the Mexican line in the United States. 



In the present study nine hundred and nine specimens have 

 been examined, four hundred and fifty of these having been 

 previously reported by Rehn and Hebard, individually or 

 jointly. We feel that the limits of distribution of each form 

 are now roughly definable for the regions being studied. Unless 

 otherwise stated the material collected by Rehn and Hebard, 

 individually or jointly, is in the collection of the author or that 

 of the Academy of Natural Sciences of Philadelphia. 



The following key includes the features by which the forms 

 here discussed may be readily distinguished. 



(Form very slender, linear. Antennae ensiform. Head horizontal, dorsal 

 length greater than that of pronotum. Pronotum with metazona one-half as 

 long as prozona or shorter; disk deplanate, with lateral and medio-longi- 

 tudinal carinae distinct and parallel. Tegmina and wings vestigial or fully 

 developed; the former, when fully developed, with apices sharply rounded, 

 nearly acute and without a fenestrate area in either sex. Caudal femora 

 with dorsal and ventral genicular angles well produced.) 



A. Head with lateral carinae of vertex overhanging the very weak lateral 

 foveolae; the latter with ventral delimiting carina very weak, but best indi- 

 cated mesad. (Pronotum with caudal margin convex, showing weak obtuse- 

 angulation.) Tegmina and wings fully developed. Male subgenital plate 

 with length nearly equal to length of preceding sternite. Dorso-external 

 genicular angles of caudal femora slightly the longer. Mountains of extreme 

 southern Arizona, southward. Achurum Saussure 



Genotype. — sumichrasti Saussure 



AA. Head with lateral carinae of vertex not overhanging the very weak 

 lateral foveolae; the latter with ventral delimiting carina very weak, but 

 best indicated distad. Tegmina and wings greatly reduced or vestigial. 

 Male subgenital plate with ventral length decidedly greater than that of 

 preceding sternite. Dorso-intcrnal genicular angles of caudal femora the 

 longer. 



B. Pronotum with caudal margin broadly convex. Tegmina and wings 



greatly reduced, overlapping; tin; former with apices well rounded in males, 



sharply rounded to different degrees in females. (Male subgenital {)late 



with length nearly twice that of preceding sternite.) Dorsal genicular angles 



of caudal femora distinctly more produced than ventral. Brownsville 



region of Texas, southwaid into eastern Mexico. 



Radinotatum minimipenne (Caudell) 



