lo Myron Harmon Sivenk 



I. Margin of pygidium tridentate, the middle tooth largest, bifid at 

 tip and bearing a median carina which extends across the pygid- 

 ium; mesoscutellum with four or two yellow spots; tubercles 

 black; legs wholly black; tegulae with a yellow spot, and a yellow 

 spot on vertex behind each eye; abdominal tergites 1-5 with 

 deep yellow bands, interrupted medially or nearly so, the lateral 

 halves deeply emarginate, breaking through on first tergite and 

 forming four spots; thorax above with pale ochreous hair; ven- 

 tral scopa silvery ; lo-ii mm psoraleae 



I. Margin of pygidium rounded with a weak tooth on each side later- 

 ally, or broadly truncate 2 



2. Mesoscutum with a yellow line over each tegula and usually with two 



yellow lines along anterior margin 3 



2. Mesoscutum without yellow lines over tegulae or on anterior margin.. 4 

 3. Legs wholly black ; clypeus black ; pygidium broadly truncate, me- 

 dially carinate and with a median bifid tooth; 11 mm. 



clypeodentatum 



3. Legs with yellow spots on the knees ; clypeus with two yellow spots 



nearly confluent with large subtriangular facial spots; pygidium 



broadly rounded, notched laterally, not carinate or medially 



toothed ; 1 1-12 mm porterae 



4. Mesoscutellum wholly black; tubercles black; tibiae with only a small 

 knee spot; front of tegulae yellow; hair of thorax above pale grayish 

 white; ventral scopa silvery gray mixed with blackish centrally; 



8 mm tenui florae. 



4. Mesoscutellum spotted ; tubercles yellow 5 



5. Clypeus and sides of face with large yellow spots; first abdominal 

 tergite merely with lateral spots ; legs more yellow ; mesoscu- 

 tellum with two yellow spots ; 10 mm nebrascense 



5. Clypeus and sides of face entirely black; first abdominal tergite 

 with a medially interrupted yellow band; legs with less yellow.. 6 

 6. Mesoscutellum with two yellow spots; tibial stripes short and narrower; 

 ventral scopa brownish white edged with fuscous; 9 mm. 



emarginatum var. 

 6. Mesoscutellum with four yellow spots ; tibial stripes broader and extend- 

 ing nearly the length of the joint 7 



7. Hair of thorax above grayish white; ventral scopa whitish ; 9 mm. 



emarginatum 



7. Hair of thorax above deep brownish ochreous; ventral scopa golden 



brown and black ; 9 mm astragali 



Males 



A broad yellow line behind eyes slightly interrupted on vertex; 15.5 mm. 



serranum 



10 



