In this group is found another interesting acarus, which is developed in man in the sebaceous crypts of the nostrils. The name of Simonea has been given to it, from Dr. Simon of Berlin, who made it his especial study. This genus leads us by its form to the Linguatulæ, the structure of which has been so long doubtful. The Simonea folliculorum belongs to the family of the Demodicidæ.
The dog harbours a demodex (D. Caninus) which causes it to lose its hair. Some years ago, the sheep in Belgium were attacked by one of the acaridæ, the Ixodes reduvius, which had been introduced from a neighbouring country, and had multiplied with frightful rapidity. Packard has given an account of an Ixodes bovis on the Erethizon epixanthus, and on the Lepus Bairdii, and an Argas Americana on cattle coming from Texas; this was published in the sixth report of the United States’ Geological survey (1873).
According to the observations of Mons. Megnin, the Tyroglyphi, the Hypopi, the Homopi, and the Trichodactyli, are transitory forms which ought not to be preserved as generic divisions among the acaridæ. We have found
on the small bat (Pipistrella) an acaride (Caris elliptica) and a new Ixodes which we have described in a special memoir on the parasites of the Cheiroptera. Mr. Lucas caught an ixodes on a dog, and kept it alive long enough distinctly to see it lay eggs which proceeded from an oviduct. These eggs formed masses attached to the abdomen of the mother.
An acarus (Dermanyssus avium) is found on birds, and multiplies with such rapidity that it completely exhausts those on which it has established itself. It has been seen accidentally on man. An instance is recorded of a woman who could not get rid of these parasites, because she passed every day through her henhouse in order to get to her cellar, and the frightened fowls threw down upon her a perfect shower of acaridæ. Not long ago mention was made at the Academy of Medicine at Paris, of a sarcoptes (S. mutans), which produces a disease among fowls, especially on the cock and hen, and which passes from these to the horse and other domestic animals. This sarcoptes prefers to live under the epidermis of the feet. Reptiles are not free from its attacks, for it is often seen on lizards and serpents. We have found a very curious one on the skin of a gecko from the south of France.
Many insects are always covered with certain species of acaridæ. Every entomologist knows that the body of the “watchman” beetle always has some of these, like little living pearls, which wander especially on the under side of the abdomen. It is the same with a small coleopterous insect that is found abundantly wherever there is any decomposing matter. Léon Dufour gave himself up to the study of some of the parasites of insects, and
mentions, among others, a species belonging to the muscidæ, the Limosina lugubris, which does not measure a line in length, and which harbours as many as fifteen pteropti under its abdomen.
Fig. 24.—Hydrachna geographica.