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



a number of coarse tubercles, each bearing a hair; they are most pronounced 

 on the dorsal surface of the scutellum and abdomen, where many of them are 

 mammillate in shape ; there are none, however, on the genae. Length about 8-11 

 mm. Larva: The third-stage larva is elliptical, broadest in the middle and 

 narrowing toward each end, which is rounded. The spinulation is character- 

 istic. The spinules are present in 3 to 4 rows on segments 3 to 5 ventrally and in 

 4 rows on segments 6 to 11 ventrally ; segment 12 is densely covered with spinules 

 ventrally. On the dorsal surface 3 rows of spinules are present on segments 

 3 to 6 ; segments 7 and 8 have small patches of them laterally. The first-stage 



larva is about 1 mm. in length, whitish, broadest in 

 the middle, and tapering toward each end. The 

 strong buccal hooks are bent near their base ; their 

 shape is clawlike rather than hornlike (fig. 60, 

 A ) . Dorsally each segment has 2 rows of spinules, 

 additional rows being added toward the sides ; ven- 

 trally, the second segment has 2 rows, the third and 

 fourth each 3, the next 6 each 4, and the last seg- 

 ment 6 rows, of spines ; the spinulation is weak 

 and transparent, and a compound microscope is 

 required to show them to advantage. The last seg- 

 ment possesses a single series of 8 to 10 median 

 Figure 63. — Rhinoestrus hooks (fig. 60, B). 

 purpureas, head of fe- Geographical Distribution.— Palaearctic Re- 



male, ventral view, show- gion: S p ain (Andalusia), France, Italy, Austria, 

 ing rudimentary probos- Rumania, Bulgaria, Greece, Morocco, Algeria, 

 * cis an d palpi. Egypt, Palestine, central and south Russia, Kazak, 



Turkestan, Semire^chje, Tadzhik, Siberia (Omsk, 

 Tomsk, Yenisseisk), Mongolia, China, Manchuria. Oriental Region : India. Eth- 

 iopian Region: Senegal, Anglo-Egyptian Sudan, Nyasaland, South Africa (rare). 



Life History and Pathogenesis. — The normal hosts are horses, 

 mules, zebras, and other Equidae. The female fly larviposits into the 

 eyes or nostrils of the host, the larvae then penetrating into the nasal 

 cavities. According to Portchinsky, each female may produce 700 

 to 800 eggs, which are deposited as larvae in lots of 8 to 40 at a time. 

 Horses are usually attacked in the autumn, the larval stage lasting 

 through the winter; the parasitism apparently causes considerable 

 discomfort and in severe cases may result in death. 



Parasitism in man seems to be similar to that by Oestrus ovis, al- 

 though only cases of ophthalmomyiasis have been recorded. In Russia, 

 man may be attacked from June to September. Infestation results in 

 a severe conjunctivitis which may last a week or more; in extreme 

 cases, according to Portchinsky (114) , the eye may be lost. In cases 

 reported by Portchinsky, from 8 to 50 larvae were removed from the 

 eye affected. As in O. ovis, the larvae are unable to develop beyond 

 the first stage in this abnormal host. 



Literature. — An extended account of this fly is given by Portchinsky 

 (117). For a discussion of the first larval stage in comparison with 

 that of Oestrus ovis, see Larrousse (80) ; for extensive descriptions 

 of the third larval and of the adult stage, see Eodhain and Bequaert 

 (183). 



The Family MUSCIDAE (Including the ANTHOMYIIDAE) 



Although the Muscidae and Anthomyiidae probably should be con- 

 sidered distinct, the line between them is rather difficult to draw. 

 For that reason the two families will be treated here under a single 

 head. This treatment is essentially that of Curran in his "North 

 American Diptera;" the Scopeumatidae (Scatophagidae), also in- 



