15S ERNEST A. BACK. 



9. Thoracic dorsum polished reddish-brown with a polished black * 

 spot on each side behind the transverse suture. Species 

 of good size. Hind femora with a narrow dark ring on the 



middle of the distal portion baclhis. 



Thorax not as above 10. 



10. Abdomen yellow; the posterior margins of the segments narrowly 



black or blackish incisularis. 



Abdomen grayish with yellowish markings, sometimes very faint, 

 on segments 2-4 flavipes. 



11. Fourth posterior cell sessile or subsessile; antennae wholly yellow, 



the third segment oval, short brevicornis. 



Fourth posterior cell petiolate 12. 



12. Dorsum of thorax with a median and two lateral stripes polished 



black ; t ground color of thorax elsewhere pinkish, but 



covered thinly with a white bloom lirgatus. 



Dorsum of thorax not as above 13. 



13. Dorsum of thorax grayish pruinose, with three brown stripes; 



antennas yellowish, the hind femora on the penultinate 

 fifth below with a conspicuous patch of white pile. 



hirtipes. 

 Hind femora without such a patch of pile 14. 



14. Dorsum of thorax very dark brown pruinose, in sharp contrast to 



the white bloom of pleurae j", antennas and occipital bristles 

 black; hind tibiae very stout and blackish on distal half. 



niiirinus. 

 Dorsum of thorax not so... 15. 



15. Hind femora and tibiae proportionally very slender 16. 



Hind femora and tibiae normal 17. 



16. Reddish-brown species with polished dorsum, lateral margins, pos- 



terior portion, pleurae, and scutellum grayish pruinose; 



wings wholly brownish obscuripennis. 



Wings hyaline; sometimes clouded at base tenuipes. 



17. Antennas and legs pale yellow; abdomen grayish with distinct or 



faint traces of yellow markings flavipes. 



Antennae rufous; third segment black on distal portion; abdomen 

 nearly uniformly brownish-black, grayish on sides, not 

 ringed; legs with blackish markings eiulieramis. 



Basal segments of antennae, the legs, and abdomen yellowish, the 

 posterior margins of the segments of the latter black or 

 blackish incisularis. 



* Sometimes of the same color as rest of thoracic dorsum, 

 t This striking contrast is not brought out in poorly preserved 

 specimens. 



