THE FLIES THAT CAUSE MYIASIS IX MAX 97 



lands. Switzerland, Italy, Sicily. Sweden, Denmark, Germany. Austria, Rumania, 

 Bulgaria, Russia (widespread). Canary Islands. Morocco, Algeria. Tunisia. 

 Egypt, Turkey. Iraq. Iran. Siberia (Tomsk. Yenisseisk. Irkutsk. Transhaikal. 

 Yakutsk. East Coast Province), Mongolia. China. Japan. Oriental Region: 

 India (Madras). Ethiopian Region: Senegal. French Guinea, Gold Coast, 

 Nigeria, Lake Tchad. Anglo-Egyptian Sudan. Eritrea, Belgian Congo, Kenya, 

 Zanzibar. South Africa (Transvaal. Cape of Good Hope). Australian Region: 

 Xew South Wales, Tasmania, Xew Zealand. Hawaii. 



Biology and Pathogenesis. — On the normal host, the horse, the eggs 

 are laid on hairs on various parts of the body, particularly on the 

 inside of the knees. They are ready to hatch in about 7 days : however, 

 hatching does not take place unless the eg<y> are rubbed by the warm 

 lip of the horse as it bites itself in an attempt to soothe the itching 

 presumably produced by the movements of the unhatched larva in the 

 eggs attached to the hairs. In the absence of such a stimulus the larvae 

 may remain alive in the eggs for as long as 3 months. The newly 

 hatched larvae adhere to the horse's moist lips and soon penetrate the 

 mucous coverings of the lips and tongue. Each female produces a 

 large number of eggs, counts by various authors ranging from 397 to 

 1,046. 



A number of cases of parasitism of man by this species in Europe, 

 particularly in Russia, are on record : cases are also known from North 

 America. According to Austmann, cases in man tend most frequently 

 to occur on the extremities. Of the species of Gasterophilus known to 

 attack man, this one apparently does so most frequently. 



Anderson (3) records a case of a larva of G. intestinaUs in the 

 posterior chamber of the eye : however, it died there and did not cause 

 any permanent damage. 



GASTEROPHILUS HAEMORRHOIDALIS (Linnaeus) 



The Nose Bot : the Nose Fly : the Red-tailed Bot 



Synonym. — Haemorrhoestrus haemorrhotdalis (Linnaeus) of Townsend's 

 Manual. 



Recognition Characters. — Adult: The head is yellow. The thorax and ab- 

 domen are mainly blackish in ground color ; the pile is chiefly pale, excepr that 

 the thorax and abdomen are each crossed by a band of black pile dorsally ; the 

 pile of tbe abdomen is reddish beyond the black cross band. The wing is un- 

 spotted; the venation is as in figure 42. Length about 12 mm. Larva: The 

 larva may be distinguished by the key characters and figures 43. C and 44. C. 

 The first-stage larvae are shorter and somewhat more robust than those of G. 

 inU stinalis; when first batched they are also somewhat smaller i about 0.59 mm.). 



Geographical Distribution. — Nearctic Region: Manitoba. Saskatchewan, 

 Alberta, British Columbia, Virginia. Illinois, Minnesota. Wisconsin. Iowa. Mis- 

 souri. North Dakota. South Dakota, Nebraska, Kansas. Montana. Idaho. Wyoming, 

 Colorado, Utah. Washington, Oregon. Neotropical Region: Venezuela. Argentina. 

 Palaearctic Region : Scotland, France. Netherlands. Italy, Corsica. Sicily. Malta, 

 Sweden, Denmark. Germany, Austria, Rumania. Bulgaria, European Russia, 

 Azerbaijan, Morocco, Turkey, Palestine. Iraq. Siberia (Tomsk. Yenisseisk. 

 Yakutsk. Transbaikal). Mongolia. China. Oriental Region: India. Ethiopian 

 Region: French West Africa. Belgian Congo. Kenya. Australian Region: Aus- 

 tralia, Tasmania, New Zealand. 



Biology and Pathogenesis. — In the normal host, the horse, the eggs 

 are deposited on hairs on the lips and around the mouth. The number 

 of eggs produced by each female is relatively small. 51 to 208, accord- 

 ing to various counts but their survival ratio is relatively high. 



The warmth and action of the saliva bring about a rapid hatching 

 in 2 to 4 days: the young larvae then penetrate the skin of the lip and 



752113°— 4S 7 



