4 U.S. NATIONAL MUSEUM BULLETIN 2 68 



10. Row of bristles on 5th sternum subequal in length to one third the width 



of the medial clypeal lobe and divided medially; 3rd tergum immaculate 



(southern Mexico) melanosa Scullen 



Row of bristles on 5th sternum subequal in length to width of medial lobe 

 of clypeus; 3rd tergum with a narrow band (southwestern states and 

 northern Mexico) melanovittata Scullen 



11. Row of bristles on 5th sternum subequal in length to one third the width 



of sternum, not divided medially (Rocky Mountain area S. to Chihuahua, 



Mexico) rubripes Cresson 



Length of bristle row on 5th sternum not over one fourth the width of the 

 sternum; bristle row divided medially 12 



12. Medial lobe on apex of pygidium extends well beyond lateral denticles (western 



Texas, southern New Mexico, and Chihuahua, Mexico) . . mellea Scullen 



Medial lobe on apex of pygidium does not extend beyond apices of the lateral 



denticles (south central Texas south into Coahuila and Nueva Leon, 



Mexico) sinuata Scullen 



13. Three subequal rows or clusters of bristles on the venter 14 



Rows or clusters of bristles on 5th sternum, if present, are either much shorter 



or different in form from those on other sterna 16 



14. Each row of bristles distinctly divided into two parts (central plains and 



eastern states) zonata (Say) 



Bristles in undivided rows 15 



15. Length about 15 mm.; scutum immaculate (Rocky Mountain area, southern 



Canada to Arizona and New Mexico) superba superba Cresson 



Length about 10 mm.; usually two short yellow stripes on the scutum (south- 

 western states, southern California, east to western Texas, north central 

 Mexico) pimarum Rohwer 



16. Bristles of the 5th sternum somewhat shorter than the others, the apical 



row itself shorter than the other rows, and the bristles of the apical row 



"waxed" into a compact layer 17 



Bristles of the 5th sternum very short, forming very short rows, evanescent 

 or absent, and, if present, not "waxed" 22 



17. Black with yellow to white markings, no amber or brown 18 



Not all black with yellow or white markings, some amber or brown 



markings 19 



18. Markings yellow; enclosure strongly ridged and with two oval patches; 



bands on terga 2, 3, 4, and 5 separated into basal and apical parts by the 

 black depressed areas (central California and western Nevada) 



insignis Provancher 



Markings creamy white; enclosure very weakly ridged and immaculate; 



complete bands on apical ridges of terga 2, 3, 4, and 5 (recorded only 



from state of San Luis Potosf, Mexico) atrata new species 



19. Background color largely black but with ferruginous bordering the yellow 



markings and on the genae (central Mexico). . zimapanensis, new species 

 Background color largely ferruginous to fuscous 20 



20. Dorsum of thorax ferruginous to fulvous with yellow markings (central 



plains from Montana S. into central Mexico, W. to southern California 



and E. to central Texas) canaliculata canaliculata (Say) 



Dorsum of thorax fuscous to dark fuscous with yellow markings .... 21 



