r -o NORTH AMERICAN DIPTBRA. 



21. Scutellum without spines; first two joints of antennae short. 



Chordonota. 

 Scutellum with spines, rarely absent in species of Odontotnyia. 22 



22 Costa thickenetl distally in front; antenna; elongate, the flagellum 



composed of six closely united segments (26 1. Analcocerus. 



Costa not thickened distally in front. ..... 23 



23. Third antenna! joint composed of four, five or six closely united 



segments. .......... 24 



Third antenna! joint composed of seven or eight closely united 

 segments. .......... 26 



24. Head strongly produced forward for insertion of the antennae, the 



face much retreating [Promeranisa, S. A.) 

 Head not strongly produced forward. ..... 25 



25. First antennal joint three or more times the length of the second 



1 13 1 Stratiomyia. 



First antennal joint less than three times the length of the second 

 (11, 12) Odontomyia. 



26. First antennal joint two or three times the length of the second, 



the third much elongated, ...... 27 



First antennal joint but little longer than the second, the third 

 terminating in a bristle Neorondania. 



27. Thorax narrowed anteriorly; body with green and yellow mark- 



ings Campeprosopa. 



Thorax not narrowed in front; body black, not with green and 

 yellow markings; posterior orbits of female often conspicuously 

 tumid ami colored (fig. 58; 17). . . . Cyphomyia. 



28. Head strongly produced anteriorly, with a porrect spine immedi- 



ately below the insertion of antennae {Rhingiopsis, S. A. 35.1 

 Head not projecting, the face produced conically downward; third 

 joint of antennae composed of six* segments ^32). 



Myxosargus. 

 CLITELLARINiE. 



29. Scutellum with spines 30 



Scutellum without spines 35 



* The j^enus Myxosargus was described by Hrauer as having eight 

 segments in the third joint of the antenna;, the segments distinguish- 

 able with difficulty. The species referred by me to this genus 

 have but six segments in the third joint, easily distinguishable. The 

 posterior orbits of the female are thin and expanded, and the females 

 of all tin- species have one or more conspicuous tubercles on the front. 



