WILLIAM G. DIETZ 109 



10. Abdomen entirely black altissima Osten Sacken 



Basal portion of abdomen red erythrophrys Williston 



11 . Thoracic stripes black 12 



Not as in the alternative 22 



12. Anterior end of the lateral thoracic stripes curved outward 13 



Not as in the alternative 19 



13. The anterior part of the lateral thoracic stripes ends in an opaque or vel- 



vety black spot 14 



Not as in the alternative 17 



14. Occiput with a shining, triangular spot 15 



Occiput opaque, yellow virescens Loew 



15. Sides of pronotal scutum, pleura and abdomen, conspicuously spotted with 



brown 16 



Prenotal scutum and abdomen yellow, pleural spots ochre yellow. 



perdita spec. n. 



16. Occipital spot broadly triangular incurva Loew 



Occipital spot narrow, prolonged anteriorly excelsior Bergroth 



17. Wings hyaline, a black spot between the antennae. 



pedunculata Loew 

 Wings yellowish-fuscous or infuscate 18 



18. Without spot between the antennae; pleura yellow, spotted black; abdo- 



men striped lineata Scopoli 



A black spot between the antennae; pleura blackish, spotted yellow; ab- 

 dominal segments two- to five-banded, black lugens Loew 



19. Wings hyaline 20 



Wings brownish penumbra Alexander 



20. Pleural spots blackish; abdomen without ventral stripe or row of spots. 



vittula Loew 

 Pleural spots at most reddish-brown; otherwise not as in the alternative. 21 



21. Occipito-frontal vitta broad; a small distinct spot above each eye; 



stigma well-defined, brown; abdomen with interrupted ventral 



stripe snowii Doane 



Occipito-frontal vitta narrow; no supra-orbital spots; stigma ill-defined, 

 pale yellowish-fuscous; abdomen with a row of black spots. 



snowii alternata subspec. n. 



22. Thorax opaque or subopaque 23 



Not as in the alternative 31 



23. Lateral margin of abdominal tergum and posterior margin of segments 



banded black macrocera virgata subsp. n. 



Not as in the alternative 24 



24. Antennae of male longer than usual, flagellar joints when bicolored, fus- 



cous at base 25 



Antennae of male not longer than usual; flagellar joints fuscous, yellow at 

 base; more rarely unicolorous 27 



25. Eighth sternite of male with two digitif orm processes 26 



Eighth sternite with a median cone-like process. 



macrocera gnata subspec. n. 



TRANS. AM. ENT. SOC, XLIV. 



