OF WASHINGTON. 93 



Abdomen bristly or hairy, in either case with regularly arranged 

 macrochaetae, sometimes spiny 6 



5. Abdomen with five or six segments, rounded or elongate, usually 



more or less flattened, but sometimes cylindrical in the 9 > 

 wings broad and large fam. Phasiidae 



Abdomen with only four segments, short oval, almost spherical, never 



flattened ; wings proportionately short and small 



fam. Gymnosomatidae 



6. Abdomen with five segments (the first often indistinct),* elongate, 



cylindrical, more rarely short oval, either gently incurvate its 

 whole length or the final segments strongly contracted and 

 drawn in ; genitalia strongly protruded 7 



Abdomen with only four segments, short oval, conical, less often 

 cylindrical, in the last case not incurvate behind and the geni 

 talia not protruded fam. Tachinidae s. str. 



7. Abdomen elongate, cylindrical, contracted at the base, incurvate its 



whole length, the last segments not conspicuously narrowed and 

 not drawn in fam. Ocypteridae 



Abdomen short oval or cylindrical, not contracted at the base, not in 

 curvate its whole length, the last segments conspicuously nar 

 rowed and drawn in fam. Phaniidae 



8. Arista bare on the apical half ;f macrochaetae present at least on the 



last two segments of the abdomen fam. Sarcophagidae 



Arista feathered or pubescent to the tip 9 



9. Abdomen cone-shaped, cylindrical or elongate oval, with macrochaetae 



on each segment ; legs usually elongate fam. Dexiidae 



Abdomen short oval, moderately broad and almost always somewhat 

 compressed, without macrochaetae on any of the segments, + at 

 most with bristly hairs on the last segments ; legs always pro 

 portionately short fam. Muscidee s. str. 



* If the first segment is indistinct, the other four segments will be 

 found always of the same length ; whereas if only the last three seg 

 ments are of equal length, then the shortened forward segment is the 

 first one. 



t Onesia, belonging in the Sat cophag idee, has the arista feathered more 

 than half its length, but may be distinguished by the macrochaetae on 

 the last two segments. 



t In very rare instances, as in a single European species of Lucilia, 

 there are macrochaetae on the middle segments. 



