INSECUTOR INSCITI^ MENSTRUUS 127 



it is an excellent specific character, for it is constant in 'a 

 species where it occurs. About the only exception to this occurs 

 in nigrovittata. The facial pile is very sparse in this species 

 and in some specimens it appears altogether absent. For this 

 reason nigrovittata is keyed in both the face bare and face 

 pilose groups. Good supplementary specific characters are 

 found in the described species so there is very little chance 

 for duplication of species in the two subgenera as they now 

 stand. Another character of considerable interest in this group 

 is the shining, deep blue color of certain species. This color 

 occurs sporadically in quite a number of cases in unrelated 

 species in both genera. Altogether eight species are so colored 

 in this tribe. 



The sexual dimorphism is so great in the Chilosini that the 

 sexes are best keyed separately. Very often species which key 

 close together are from widely separated parts of the country. 

 For this reason localities are given in the keys. 



A. Eyes hairy ; antennal pits separated (type Aavipes) Chilosia. 



a. Face bare subgenus Chilosia males 1, females 1 



aa. Face hairy subgenus, 



new (type occidentalis Will.) Chilomyia males 13, females 17 



B. Eyes bare ; antennal pits confluent Cartosyrphus. 



Arista long plumose sub- 

 genus, new (type willisfoni Snow). Hiatomyia males 1, females 1 



Arista pubescent to bare, 



subgenus (type pagana) Cartosyrphus males 8, females 12 



Chilosia — Males 

 Eyes hairy; antennal pits separated 



1. Face bare subgenus Chilosia 2 



Face hairy subgenus Chilomyia 13 



2. Large (about 12 mm.), robust species, clothed with long pile; 



no bristle-like hairs on thorax ; head triangular in shape ; 

 posterior cross-vein as long or longer than ultimate section 



of apical cross-vein 3 



Pile short, usually bristle-like hairs present on thorax ; head 

 broadly oval ; posterior cross-vein shorter than ultimate sec- 

 tion of fourth vein 6 



3. Shining bronze species, with abundant golden pile (Mexico) 



citi-ysoclilainys Will. 

 Not shining bronze 4 



