For both species of _Hypoderma_ there are numerous cases on record of their occurrence in man. Hamilton (1893) saw a boy, six years of age, who had been suffering for some months from the glands on one side of his neck being swollen and from a fetid ulceration around the back teeth of the lower jaw of the same side. Three months' treatment was of no avail and the end seemed near; one day a white object, which was seen to move, was observed in the ulcer at the root of the tongue, and on being extracted was recognized as a full grown larva of _Hypoderma_. It was of usual tawny color, about half an inch long when contracted, about one third that thickness, and quite lively. The case resulted fatally. The boy had been on a dairy farm the previous fall, where probably the egg (or larva) was in some way taken into his mouth, and the larva found between the base of the tongue and the jaw suitable tissue in which to develop. Topsent (1901) reports a case of "creeping myasis" caused by _H. lineata_ in the skin of the neck and shoulders of a girl eight years of age. The larva travelled a distance of nearly six and a half inches. The little patient suffered excruciating pain in the place occupied by the larva. _Hypoderma diana_ infests deer, and has been known to occur in man. _Oestris ovis_, the sheep bot-fly, or head maggot, is widely distributed in all parts of the world. In mid-summer the flies deposit living maggots in the nostrils of sheep. These larvæ promptly pass up the nasal passages into the frontal and maxillary sinuses, where they feed on the mucous to be found there. In their migrations they cause great irritation to their host, and when present in numbers may cause vertigo, paroxysms, and even death. Portschinsky in an important monograph on this species, has discussed in detail its relation to man. He shows that it is not uncommon for the fly to attack man and that the minute living larvæ are deposited in the eyes, nostrils, lips, or mouth. A typical case in which the larvæ were deposited in the eye was described by a German oculist Kayser, in 1905. A woman brought her six year old daughter to him and said that the day before, about noontime, a flying insect struck the eye of the child and that since then she had felt a pain which increased towards evening. In the morning the pain ceased but the eye was very red. She was examined at about noon, at which time she was quiet and felt no pain. She was not sensitive to light, and the only thing noticed was a slight congestion and accumulation of secretion in the corner of the right eye. A careful examination of the eye disclosed small, active, white larvæ that crawled out from the folds of the conjunctiva and then back and disappeared. Five of these larvæ were removed and although an uncomfortable feeling persisted for a while, the eye became normal in about three weeks.