[Hydrotæa meteorica, L. (the meteoric fly). This fly attacks man as well as animals. They especially bite around the eyes and nostrils of animals, but are not so particular with man; the head, however, is usually chosen. Linnæus called it the meteoric fly because it often forms clouds around horses’ heads at the approach of rain. The Hydrotæas are usually black or blue-black in colour with bare eyes and simple abdomen, the front femora peculiarly constructed. H. meteorica, L., occurs in Britain.
[The members of the genus Hydrophoria, Desvoidy, also bite man.
Pupipara or Eproboscidæ.
[The Pupipara are all blood-suckers, the majority occurring as parasites on mammals and birds, where they are more or less permanent parasites. Occasionally some may attack man. They all produce their young fully formed, and they assume the pupal stage immediately after extrusion. The puparia are large. They are mostly flat, louse-like flies which may or may not be winged. In the case of Melophagus I have found the puparia are often passed by the female. The winged forms have a short quick flight, and when disturbed will seek shelter in man’s hair or beard. Two main families occur: (1) the Hippoboscidæ, and (2) the Nycteribiidæ. The former occur on animals and birds, the latter on bats only, but may invade man. Two other families are known—the Braulidæ (bee parasites) and the Streblidæ (bat parasites).
[The mouth of the Hippoboscidæ is long and sharp, forming a proboscis. The thorax and abdomen are flat and leathery. The legs are stout and strong, and terminate in large dentate claws and other structures of use in holding on to the hair or feathers of their host when blood-sucking.
[Austen says it is probable that the Hippoboscidæ are descended from ancestors belonging to the Muscidæ, which underwent modification in bodily structure as the consequence of the adoption of a parasitic mode of life.
[Two wings are present in the true Hippoboscæ, Hippobosca equina (of the horse), H. camelina (of the camel), H. maculata (of oxen), and H. capensis (of dogs), but are absent in Melophagus, the sheep tick or ked fly (M. ovinus).
[In two genera, Lipoptena and Echestypus, wings are at first present, but are lost as soon as the fly finds its permanent host.
[With regard to their biting man, such is only occasional. I have known sheep shearers to be badly bitten by Melophagus ovinus, and have more than once been attacked myself when standing where shearing is taking place. Sharp records the grouse parasite, Ornithomyia lagopodis, as once biting severely a gamekeeper in Scotland. There are also records of H. maculata biting man in Africa and India.
[Although so far not connected with any human disease, it is interesting to note Theiler has shown that Hippobosca rufipes, v. Olfers, and H. maculata, Leach, are capable of transmitting Trypanosoma theileri, Laveran, the cause of gall sickness amongst cattle in the Transvaal. It is now considered, however, that Trypanosoma theileri is non-pathogenic, and that the cause of gall sickness is a piroplasma-like organism known as Anaplasma marginale. Theiler, Laveran and Mesnil all hold this view (vide Laveran and Mesnil, “Trypanosomes and Trypanosomiases,” second edition, 1912, p. 330).