16 Everett E. Wehr 



Arista rarely long plumose for one-half its length or more, in 

 such cases some (certain species of Eristalis) may be excluded 

 by the closed marginal cell; others (certain Chilosia) can be ex- 

 cluded by the absence of yellow body markings or yellow pile, 

 and by having the anterior cross-vein placed well before middle 

 of discal cell; finally, the prongs of the genitalia are similar 7 



7. Very large yellow and black species; the post stigma very 

 elongate, being very nearly twice as long as broad; marginal 

 cell closed; third vein with a downward loop into first posterior 

 cell (discal cell. Shannon) ; sixth vein recurrent beyond anal 

 cell; shape of head, position of antennae and length of arista 

 similar to the Xylota type, but the face is broadly covered with 

 loose pile (Milesia only) Milesinae 



Length of post stigma one and one-half times or less that of 

 width, and otherwise without above combination of characters.... 8 



8. Third longitudinal vein with a deep downward loop into first 

 posterior cell (discal cell, Shannon) ; face except for a medium 

 stripe, clothed with long pile; sixth vein entering margin of 

 wing or short distance beyond anal cell, i. e., usual distance; 

 thorax never bearing bristles; marginal cell closed in Eristalis 

 and Meromacrus , Eristalinae 



Third longitudinal vein usually straight, but in such cases where 

 i tis looped downwards {Pterallastes and Teuchocnemis) the 

 face is bare, except for a few hairs along eye margins, and sixth 

 vein is prolonged well forward beyond anal cell. (The bare 

 face also excludes Tropidia and Syritta from Eristalinae, while 

 the bristles on the thorax and the brassy color excludes 

 Chrysochlamys 9 



9. Anterior cross- vein placed well before middle of discal cell; 

 third vein always straight; antennae sometimes with terminal 

 style {Callicera and Pelecocera) Chilosinae 



Anterior cross- vein joining discal cell at or beyond middle; face 

 rarely covered with pile and in such cases third vein is always 

 straight Xylotinae 



Syphinae 

 key to the tribes 



1. Face black, scutellum entirely aeneous or blacA; Melanostomini 



122 



