OCCURRENCE. 11 



de la Societe Entomologique de France there are good figures by 

 Laboulbene of Teichomyza and some other species. 



Interest in tiie larvae and the life history of these species of flies 

 arises also from their medical and sanitary importance. The famous 

 tsetse flies (Olossina spp.) of Africa are related to tlie stable fly. One 

 of these flies distributes the Nagana disease of cattle, while another 

 species disseminates the sleeping sickness of man. The Congo floor- 

 maggot is also related; this species inhabits the huts of the natives, 

 and at night crawls from the cracks to attack and suck blood from 

 sleeping persons. The Bcngalia fly is also related; it deposits eggs 

 or larviB on the skin of man and dogs in Africa. But the house fly 

 is by far the most injurious species, since its habits are such that the 

 germs taken up by its proboscis from sputum and dejecta are scat- 

 tered over food about to be eaten by man. 



There are also various species of these flies injurious to domestic 

 animals; notably the horn fly, which is a serious pest to cattle. The 

 stable fly annoys cattle, and the sheep maggot (Lucilia sericata) 

 injures both the sheep and the wool. The screw-worm, or heel fly, is 

 a serious pest of cattle, and also attacks man. 



The occurrence of dipterous larvae in man is known as "myiasis." 

 Various divisions are given; as "myiasis externa" or "myiasis der- 

 matosa," for those in the skin or wounds; "myiasis intestinalis," 

 for those in the alimentary canal; "myiasis narium," for larvae in 

 the nose; etc. The occurrence of larvae in the nose in this country is 

 rather accidental, and usually due to the screw-worm. In tropical 

 countries such cases are much commoner, and in the East Indies a 

 disease known as "Peenash" is due to larvae in the nose. 



A great number of papers has been published on the medical side 

 of myiasis, often with some description of the maggot, but it is not 

 necessary to list them here. 



These maggots, as previously stated, usually do not cause any 

 trouble, but Alessandrini has shown in a study of the cheese skipper 

 that these larvae may cause intestinal lesions in a dog. The vitality 

 of these larvae is such that they are not readily affected by the diges- 

 tive fluids, and in fact are resistant to many chemical substances that 

 one would suppose fatal to them. It is therefore perfectly possible 

 for these larvae to continue their development in the intestine, 

 especially in cases of constipation. 



No other group of insects affects human health and human interests 

 more seriously or directly than the flies of the Muscidae and Sarcoph- 

 agidae. It is therefore of the greatest importance that the larvae 

 of tliese flies should be studied in order that it may be j)ossible to 

 distinguish them with accuracy. 



