148 MISC. PUBLICATION 631, U. S. DEPT. OF AGRICULTURE 



Oklahoma, Texas, Arizona, California. Neotropical Region : Mexico, Guatemala, 

 Honduras, Nicaragua, Costa Rica, Panama, Canal Zone, Bahama Islands, Cuba, 

 Jamaica, Haiti, Dominican Republic, Puerto Rico, Guadeloupe, Martinique, Bar- 

 bados, Trinidad. Colombia, Ecuador, Venezuela, British Guiana, French Guiana, 

 Brazil, Peru. Bolivia, Paraguay, Uruguay. Argentina. Palaearctic Region : Malta. 

 Australian Region : Samoa, Guadalcanal, Bougainville, Hawaiian Islands. 



Biology and Pathogenesis. — The larvae breed in various sub- 

 stances, such as decaying fruits and vegetables, catsup, animal 

 cadavers, and the wax, honey, pollen, and waste materials found in 

 beehives. They are remarkably hardy. In the southern part of the 

 United States they are common in outdoor privies. 



Several cases of intestinal myiasis in man, apparently authentic, 

 have been reported, the large and vigorous larvae causing rather 

 severe gastrointestinal disturbances. 



& v 



The Family THEREVIDAE 



The Stiletto Flies ; the Snipe Flies 



The Therevidae form a family of predaceous flies of medium size. 

 Some of them resemble certain Asilidae, but they may readily be dis- 

 tinguished by the fact that the vertex is not excavated, as it is in that 

 family; others are bombyliidlike, but, unlike the members of that 

 family, have five posterior cells (fig. 3). The larvae, like the adults, 

 are predaceous. They live in fungi, rotten tree trunks, and soil; some 

 are said to parasitize Lepidoptera. 



The Palaearctic species have been treated in Lindner's "Die Fliegen 

 der Palaearktischen Region." 



The Genus THEREVA Latreille 



This is a genus of typically furry or hairy species ; the paraf acials 

 are pilose; the first antennal segment is slender and much shorter 

 than the length of the head. Cell r 4 takes in the wing apex; cell r 5 

 is not divided by an extra cross vein beyond the furcation of vein r 4+5 . 



THEREVA NOBILITATA Fabricius 



This is a variable species in a difficult genus, and to attempt to give 

 distinguishing characters in a limited space would serve no useful 

 purpose. 



Geogeaphical Distkibtjtion. — Palaearctic Region : Scotland, England, Spain, 

 France, Netherlands, Switzerland, Italy, Capri, Corsica, Sweden, Finland, Lap- 

 land (Swedish), Denmark, Germany, Czechoslovakia, Austria, Hungary, Yugo- 

 slavia, European Russia, Turkestan. 



Pathogenesis. — Austen (S) records a case in England of a larva of 

 a species of Thereva, probably nohUitata, being ''coughed up by a 

 man who had 'complained of a bad throat' for about a week," and 

 cites a previous case in Germany where a 2-weeks' illness ceased after 

 the patient had vomited a living larva of T. nob'rfitata. 



The Family SYRPHIDAE 



The Hover Flies and Drone Flies 



Members of this family are typically medium-sized flies of dark 

 color, with bright tegumentary spots or bands on the body; many, 

 however, vary from this general color scheme. A character which 



