190 SANITARY ENTOMOLOGY 



forest regions of Africa. Man is an accidental host, the species normally 

 infesting thin skinned wild mammals. According to Rodhain and 

 Bequaert, who have given much attention to the biologies of this and 

 related species, the eggs are deposited on the ground in the burrows fre- 

 quented by the animals, the larvae hatch out and penetrate the skin when 

 the hosts are lying upon them. The larvoe develop within the host in 

 twelve to fifteen days. The pupal stage, which is passed in the ground, 

 ranges from twenty-three to twenty-six days, the life cycle being about 

 forty days. Another Muscid genus, Bengalia (especially B. depressa 

 Walker) , causes cutaneous myiasis in man in Rhodesia and other parts of 

 Africa. The eggs are deposited on the clothing or person of man and 

 on the hair of animals. 



Another interesting form is Neocuterehra squamosa Griinberg, which 

 develops in the adipose tissues in the soles of the feet of the African 

 elephant. 



INTESTINAL AND UROGENITAL MYIASIS 



There is every reason to believe that myiasis of the intestinal tract 

 and urogenital openings results largely from careless modes of living. 

 The types of myiasis included in this group should not be confused with 

 urogenital myiasis caused by Chrysomya and related forms. A large per- 

 centage of these cases is purely accidental and there is no doubt that a 

 great many larvae are ingested with food which never produce symptoms 

 to attract attention to their presence. Several different families of flies 

 have been recorded as causing intestinal myiasis, one of the most com- 

 mon being the rat-tail larvae of the family Syrphidae. Records of intes- 

 tinal myiasis due to Sarcophagidae are also numerous, but it should be 

 borne in mind, especially with this fly, that there are many opportunities 

 for mistakes. With little doubt, in many instances, the larvae are not 

 passed, but are deposited in the excrement by flies which have the habit of 

 visiting and depositing larvae almost instantly after defecation. 



The whole group may be subdivided into those forms which are directly 

 parasitic, such as horse bots, and others which are more or less acci- 

 dental. 



America. — The importance of the horse bots in infesting equines is 

 such that brief discussion is necessary. In this country there are three 

 species, all of which are of considerable economic importance. These are 

 the common horse bot, Gastrophilus intestinalis DeGcer, the chin fly or 

 throat bot fly, G. nasalis Linnaeus and the nose fly, G. liaemorrhoidalis 

 Linnaeus (plates X, XII). These three species are widely distributed 

 throughout the world and were met with as pests in many of the recent 

 war theaters. Certain other species are also present in European and 

 Asiatic countries but these are of less impoi'tance. 



