KEY TO DIPTERA. 



27. Frontal lunule and suture (ptilinum) almost always 

 distinct. Head and thorax very often with bristles. 

 Third antennal joint usually with dorsal arista. Second 

 basal cell as a rule separated by a cross- vein from a com- 

 plete discal cell. Numerous Muscoid families. See p. 258 

 and following pages. 



No frontal suture. Second basal cell often confluent 

 with the discal cell, or the discal cell absent. Usually 

 small flies 28. 



28. For the most part brilliantly colored (metallic green) 

 flies. Arista of the antennas dorsal or terminal. Second 

 basal cell merged with the discal cell DOLICHOPODID^; 



(P- 2 50. 

 Color not brilliantly green. Arista of the antennas 



usually terminal. Second basal cell rarely merged with 

 the discal cell EMPIDID.E (20). 



29. Between the third and fourth longitudinal veins and 

 subparallel with them a spurious longitudinal vein, which 

 is rarely absent. Usually brightly colored flower-flies, 

 rarely with bristles SYRPHID^E (p. 253). 



No extra vein between the third and fourth longitudi- 

 nal veins 30. 



30. Proboscis elongate and slender, often folding. No 

 bristles on head and thorax CONOPID^E (p. 257). 



Proboscis short, not projecting. Small flies 31. 



31. Antennae with terminal arista. Head and thorax 

 with bristles PLATYPEZID.E. 



Antennas with dorsal arista. Head and thorax with- 

 out true bristles. Wings much longer than the abdomen. 



. PIPUNCULID.E. 



235 



