PROC. ENT. SOC. WASH., VOL. 21, NO. 9, DEC., 1919 205 



4. A cross-vein connecting subcosta and first branch of radius; proboscis 



not geniculated at middle 5 



No cross- vein connecting subcosta and first branch of radius; these 

 veins sometimes slightly fused at apices; proboscis geniculated at or 

 near middle as well as at base 6 



5. Femora without short thorns on apical half of antero- and postero-ven- 



tral surfaces; first posterior cell open, or closed at extreme apex; 

 palpi very small, not longer than diameter of proboscis at their bases 



Zodion Latreille 



Femora with some short thorns on apical half of antero- and postero- 

 ventral surfaces; first posterior cell long-stalked; palpi long, about 3 



times as long as diameter of proboscis at their bases 



Robertsonomyia gen. n. 



6. Femora without short thorns on apical half of antero- and postero-ven- 



tral surfaces; anal cell short, basal section of fifth vein not longer 



than apical Dalmannia Robineau-Desvoidy 



Femora with short thorns on apica! half of antero- and postero-ventral 

 surfaces; anal cell elongate, basal portion of fifth vein much longer 

 than apical 7 



7. Hind coxae bare on their inner posterior margin; cheek as high or al- 



most as high as eye Myopa Fabricius 



Hind coxae with some hairs on inner posterior margin; cheek not nearly 

 as high as eye Occemyia Robineau-Desvoidy 



Robertsonomyia, gen. n. 



The relationships and distinguishing characters of this genus 

 are given in the synopsis. The genus is undoubtedly closely 

 allied to Zodion but possesses many of the characters of Occemyia . 



Genotype. Zodion palpalis Robertson. 



The type and only species of this genus has been recorded only 

 from Illinois by Mr. Charles Robertson, in whose honor the genus 

 is named. 



( . 1 final date 'af publication f)cce.iher 8, 1 '. M ' i 



