131 



Family Scatopsidse — The Minute Black Scavengers 



Small black or brownish flies, the appendages and thorax often 

 partly yellowish. 



Head more or less orbicular — subquadrate or elonp;ate oval; antcnnjB 

 composed of seven to twelve seo-ments; iisnally sliglitly longer than the 

 head; three ocelli; proboscis short and stont. Thorax gently convex, 

 rarely flattened. Legs short, the femora robust. Wings with the veins 

 thin, the first and third strong, the second simulating a crossvein, the 

 fourth vein furcate or simple. Abdomen subcylindrical, composed of 

 six or seven segments, the male genitalia large. 



The Scatoi^sida^ breed m decaying vegetable and animal matter and 

 excrement. They often breed in sewers and privies and frer[uently 

 become very numerous in houses, where they cause more anxiety than 

 liarm. In the autumn tliey are frequently common on windows, when 

 they are most easily collected. TJie species range in size from .75 to 3 

 mm. in length and the family may be readily recognized by the wing 

 venation. Mclander* has revised the North American species. 



KEY TO GENERA 



1. Wings of normal size 2 



Wings about half normal size, the adults flightless (4). 



Cobaldia Melander 



2. Front tibiae ending in a spur (.5) Aspistes Meigen 



Front tibiae without apical spur 3 



3. Anterior branch of the fourth vein without appendage 4 



Anterior branch of the fourth vein with an appendage near the base 



on the anterior side (12) Scatopse Geoffroy 



4. Anterior branch of the fourth vein not disconnected at the base (10). . 5 

 Anterior branch of the fourth vein disconnected basally (7) V 



5. Petiole of the fourth vein more than twice as long as the anterior 



branch (10) Swammerdaniella Enderlein 



Petiole of the fourth vein at most a little longer than the anterior 

 branch G 



* 1916, Bull. 130, state Coll. Wash.. Agric. Exp. Station. 



Scatopsidse I. — 1, 2. 3. Rhegmoclema atrata, larva, pupa, adult; 4, Coboldia foritiicarum ; 

 5, Aspistes berolinensis ; 6, Pscctrosciara californica. 



