THE FLIES THAT CAUSE MYIASIS IX MAX 



101 



is short and cylindrical, with small hut evident lahella and without palpi. The 

 wings and squamae are pale brownish, the legs mainly yellow. The propleura 

 are clothed with distinct hairs; the pile of the abdomen, except at its base, 

 is very short. The ventral memhrane of the abdomen is distinctly exposed. 

 Larva: The first-stage larva (hg. 4S) is snbcylindrical, somewhat narrower be- 

 hind: the third and fourth segments are thickly set with small spines; the fifth 

 to seventh segments have, in addition to the smaller spines, each a ring of 

 heavy spines which usually occur in a single row ventrally and a double one 

 dorsally ; the eighth to twelfth segments are bare. After the first molt (fig. 49), 

 the larva becomes pyriform, the bare posterior segments remaining narrow, but 

 the more heavily spined anterior end becomes ovate to globular. The mature 

 larva (fig. 50) is elongated-ovate, with the heavy spines somewhat reduced; the 

 posterior spiracles are sunken in a cavity and consist each of three slits and 



Figtjbe 47. — Dermatobia hominis, adult female. 



no button; the anterior spiracles are prominent, elliptical, and flowerlike in 

 appearance. 



Geographical Distribution. — Widespread, but confined to the Neotropical 

 Region. Mexico (northward to Tamaulipas), Guatemala, British Honduras. 

 Honduras, Costa Rica, Panama, Canal Zone, Trinidad, Colombia, Ecuador, Vene- 

 zuela. British, French, and Dutch Guiana. Brazil (widespread), Peru, Paraguay, 

 Chile, Argentina (northern part. Tucuman to Santa Fe and northward). Appar- 

 ently absent from the Windward and Leeward Islands and the Antilles. 



Biology and Pathogenesis.— This is primarily a forest species ; it 

 occurs chiefly in the wooded tracts and forest margins of the lowlands 

 and river valleys, but it may range up to an altitude of 3,000 feet. 

 This fly employs an interesting and unique method of insuring trans- 

 portation of its eggs to the host. The adult female captures other 

 Diptera and glues her eggs to their abdomens (fig. 51), the load appar- 

 ently being gaged by the carrier's ability to transport them. The car- 

 riers chosen are day-flying mosquitoes (Psorophora) , stabletlies 

 (Stomoosys), Synth siomyia, and other Diptera that frequent the hosts 

 of Dermatobia; rarely ticks are used in this way. When no carrier is 



