Chrysomyia macellaria, (= Compsomyia), the "screw worm"-fly is one of the most important species of flies directly affecting man, in North America. It is not normally parasitic, however, and hence will be considered with other facultative parasites in Chapter IV.
Auchmeromyia luteola, the Congo floor maggot. This is a muscid of grewsome habits, which has a wide distribution throughout Africa. The fly ([fig. 86]) deposits its eggs on the ground of the huts of the natives. The whitish larvæ ([fig. 85]) on hatching are slightly flattened ventrally, and each segment bears posteriorly three foot-pads transversely arranged. At night the larvæ find their way into the low beds or couches of the natives and suck their blood. The adult flies do not bite man and, as far as known, the larvæ do not play any rôle in the transmission of sleeping sickness or other diseases.
This habit of blood-sucking by muscid larvæ is usually referred to as peculiar to Auchmeromyia luteola but it should be noted that the larvæ of Protocalliphora frequent the nests of birds and feed upon the young. Mr. A. F. Coutant has studied especially the life-history and habits of P. azurea, whose larvæ he found attacking young crows at Ithaca, N.Y. He was unable to induce the larvæ to feed on man.
Cordylobia anthropophaga, (Ochromyia anthropophaga), or Tumbu-fly ([fig. 87]) is an African species whose larvæ affect man much as do those of Dermatobia cyniventris, of Central and South America. The larva ([fig. 88]), which is known as "ver du Cayor" because it was first observed in Cayor, in Senegambia, develops in the skin of man and of various animals, such as dogs, cats, and monkeys. It is about 12 mm. in length, and of the form of the larvæ of other muscids. Upon the intermediate segments are minute, brownish recurved spines which give to the larva its characteristic appearance. The life-history is not satisfactorily worked out, but Fuller (1914), after reviewing the evidence believes that, as a rule, it deposits its young in the sleeping places of man and animals, whether such be a bed, a board, the floor, or the bare ground. In the case of babies, the maggots may be deposited on the scalp. The minute maggots bore their way painlessly into the skin. As many as forty parasites have been found in one individual and one author has reported finding more than three hundred in a spaniel puppy. Though their attacks are at times extremely painful, it is seldom that any serious results follow.