KEY TO MAJOR TAXONOMIC UNITS OF 
NORTH AMERICAN MUSCOID AND 
CALLIPHORID FLIES 
1. Second antennal segment without a laterodorsal longitudinal 
seam; thorax without a complete transverse suture on dor- 
sum anterior to wings; abdominal spiracles 1 to 5 lo- 
cated in membrane (except in Chloropidae and Ephydri- 
dae); lower calypter normally undeveloped; posthumeral 
bristles absent; postalar callosity normally undeveloped; 
anterior orbits usually separated above from lateroverti- 
eal plates or latter alone are developed and bear fronto- 
orbital bristles (if frontoorbital bristles are located on 
orbits, the lower bristles are closer to eye margin than 
upper); subcostal vein often incomplete or imperfect; 
fourth. veiny usually straightwasc.. .. >. #.. Acalypteratae. 
Second antennal segment with a complete laterodorsal 
longitudinal seam; thorax normally with a complete 
transverse suture on dorsum anterior to wings; abdominal 
spiracles 2 to 5 located in tergites (except in Glossinidae) ; 
lower calypter usually large; posthumeral bristles usually 
present; postalar callosity usually developed; anterior 
orbits not separated above from laterovertical plates and 
bearing a row of converging frontoorbital bristles which 
are more distant from eye margin toward lunule than 
toward vertex; subcostal vein always distinct and ending 
anmeostalavellt cys, stl al ea Aone losis « Calypteratae....2 
2. Hypopleuron usually without hairs or bristles below meta- 
thoracic spiracle; pteropleuron usually without vestiture; 
when three sternopleural bristles present, these usually 
arranged 1 + 2; ventral abdominal membrane more or less 
exposed, usually distinct; fourth longitudinal vein straight 
or but slightly curved, and usually extending to wing 
margin behind wing apex.............. Anthomyiaria. 
Hypopleuron usually with hairs or bristles in one or 
more rows below the metathoracic spiracle; pteropleuron 
usually pilose or setose; when three sternopleural bristles 
present, these usually arranged 2 +- 1; ventral abdominal 
membrane usually hidden; fourth longitudinal vein ecurv- 
ing or bending forward, most often narrowing the apical 
CE eG ates cere oe: Oestromusearia. 3 
4] 
