THE FLIES THAT CAUSE MYIASIS IN MAN 



115 



Figure 61. — Oestrus ovis, 

 head of female, ventral 

 view, showing rudimentary 

 proboscis and palpi. 



small tubercles, each bearing a hair. The legs are yellow. The wings are but 

 little longer than the thorax and comparatively broad, the apical cell being about 

 three times as long as broad. The abdomen is black, with a pattern of irregular 

 grayish spots, which appear to change with the light incidence. Length 10-12 mm. 

 Larva : The larva is distinguishable only with difficulty from other members of 

 the genus, but is readily distinguishable from Rhinoestrus purpureus, the only 

 other oestrid known to be of medical importance. 



In. the whitish, robust, third-stage larva spinulo.se areas are absent from the 

 head and from the dorsal surface of the body : on 

 the anterior margin of the ventral surface the 

 third segment bears one to two rows, the fourth 

 and fifth each two to three rows, the sixth and 

 seventh each three to four rows, the eight, ninth, 

 tenth, and eleventh each four to five rows, and the 

 twelfth (anal) segment two rows. 



The first-stage larva is a small, white elon- 

 gate-oval creature, about 1 mm. in length. The 

 strong buccal hooks (fig. 59, A) are recurved and 

 hornlike, the strong bend beginning slightly be- 

 fore the middle; the last segment (fig. 59, B) 

 bears 2 prominences, each of which possesses 10 

 or 11 (sometimes 9) hooklets : the shape of each 

 hooklet has been compared by Portchinsky to the 

 tooth of a shark. The spinulation of the seg- 

 ments is weak and hard to see, except from pre- 

 pared slides; the arrangement of the spines, according to Larrousse (80), is as 

 follows : Dorsally, the third segment has 3 row,s of spines anteriorly ; each of the 

 others has 2 complete rows, with a partial row in the middle consisting of 8 to 12 

 spines; the number of rows increases laterally. Ventrally, each segment has 3 

 rows of spines, the last segment sometimes with an incomplete fourth. The 



posterior spiracles are re- 

 duced to small rounded 

 openings, barely visible and 

 not encircled by sclerotized 

 plates. 



Geographical Distribu- 

 tion. — Practically world- 

 wide, wherever native or 

 domestic sheep and goats 

 are found. Nearctic Re- 

 gion : Ontario, Alberta, 

 Maine, New Hampshire, 

 Massachusetts, Connecticut, 

 New York, New Jersey, Vir- 

 ginia, Georgia, Florida, 

 Mississippi, Ohio, Michigan, 

 Kentucky, Minnesota, Iowa, 

 North Dakota, Texas, Mon- 

 tana, Wyoming, Colorado. 

 Utah, Nevada, New Mexico, 

 Arizona, Washington, Ore- 

 gon, California. Neotropi- 

 cal Region : Mexico, Puerto 

 Rico, Brazil (Rio de Ja- 

 neiro and southward), 

 Peru, Uruguay, Chile, Ar- 

 gentina. Palaearctic Region: Ireland, Scotland, England, Spain, France. Nether- 

 lands, Switzerland, Italy, Corsica, Sardinia, Sicily, Denmark, Germany, Czechoslo- 

 vakia, Austria, Yugoslavia, Bulgaria, Greece, European Turkey, European Russia, 

 Cape Verde Islands, Canary Islands, Morocco, Algeria, Tunisia. Libia, Egypt, 

 Cyprus, Syria, Palestine, Iraq, Iran, Kazak, Turkestan. Tadzhik, "Transcaspia," 

 Semiretschje, Mongolia, China. Oriental Region: India (widespread), Taiwan. 

 Ethiopian Region: Senegal, Nigeria, Anglo-Egyptian Sudan, Belgian Congo, 

 Kenya, Tanganyika, Zanzibar, Mozambique, South-West Africa, South Africa 

 (Basutoland), Mauritius, Rodriguez. Australian Region: South Australia, 

 Queensland, Tasmania, New Zealand, Hawaiian Islands. 



Figure 62. — Oestrus ovis, adult female. 



