102 D. W. COQUILLETT. 



3. — Scutellum wholly opaque 4. 



Scutellum shining »tra<liilsi Loew. 



4. — Pile of autennse and face largely black, wings blackish in front 5. 



Pile of antenna-, head, thorax and scutellum white or yellowish: wings 



hyaline, the cross-veins bordered with brown liiubatsi Loew. 



5. — Pile of thorax and scutellum largely black, costa of male furnished with 



teeth-like projections serrata n. sp. 



Pile of thorax and scutellnm largely yellowish, costa destitute of teeth-like 



projections iiielanocerala Bigot. 



6. — Abdomen having each segment partly opaque 7. 



Abdomen, except first segment, wholly shining greenish blue, halteres black. 



ainabilis O. S. 



7. — Knob of halteres partly or wholly yellow 8. 



Knob of halteres wholly black, pile of auteunse and face black. 



obesula Loew. 

 8. --Pile of thorax and basal half of abdomen wholly yellowish red. 



rufula O. S. 

 Pile of thorax and abdomen mixed black and yellowish. 



iiigripeiiiiis Loew. 



Ploas serrata n. sp. % 9. — Opaque black, the halteres yellow. Pile of 

 antennae, face, lower half of occiput (usually) and many on upper half, on tho- 

 rax, scutellnm and abdomen black, that on upper half of occiput, on chin, coxse 

 and on sides of basal half of abdomen largely yellow, that on sides of thorax in 

 the female yellow; appressed tomentum of head and body yellow. Wings hya- 

 line, the base smoky brown, this color gradually evanescent posteriorly, leaving 

 a brown cloud on veins at bases of first and fourth posterior cells; costa of male 

 furnished with small, teeth-like projections. Length 6-11 mm. 



Southern California. Seven males and seven females in April, 

 INIay and December. 



P91THIRIA Meigen. 



The following table contains all the sjjecies known to occur in this 

 country north of Mexico. 



1. — Wings, except sometimes in the costal cell, hyaline 2. 



Wings marked with brown clouds or spots 8. 



2. — Body more or less black 3. 



Body wholly yellow, only the proboscis and tips of tarsi black, 



sulpliiirea. 

 3. — Head, thorax and sometimes the abdomen marked with yellow (females). ..4. 



Head, thorax and abdomen wholly black 6. 



4. — Antenna; black, sides of face not spotted 5. 



Antennae largely yellow, sides of face marked with two black spots (four in 



all) nolala. 



5. — Scutellum and dorsum of thorax wholly black llorale n. sp. 



Scutellum partly yellow II. 



6. — Thorax and scutellum opaque 7. 



Thorax and scutellum shining, pile of head and body white. 



di versa u. sp. 



