Page:Popular Science Monthly Volume 14.djvu/523

Rh Linnæus described a mite under the name Acarus dysenteriæ, to the presence of which was ascribed a persistent dysentery that attacked one of his pupils, and some later authors have thought it may have been the cheese-mite, or some of its allies; but this is improbable. Cheese-mites are constantly eaten in great quantities, and, so far as can be judged, with perfect impunity; if they did cause mischief, numerous cases would have been noted and reported, whereas there are none recorded. A mite is also found in flour, sometimes in abundance; Hassell, however, says it is never present unless the flour is damaged. Assuming it to be a separate and distinctive species, it was described by Linnæus and named A. farinæ, and has been so figured and spoken of by naturalists down to the present time. But Mr. Andrew Murray, whose excellent hand-book on "Economic Entomology" is freely used in this article, asserts that the flour-mite and the milk-mite are not distinct species, but are identical with the cheese-mite. Not, he explains, that every species found on cheese or flour is this species—for both are doubtless infested with others—but that the old authors have made two or three species out of one. The cheese-mite has been met with in very old linseed-meal, and has been found on wounds that had been dressed with poultices made of linseed-meal. Of course, its presence under such circumstances must be mischievous. Another species which lives on cheese, T. longior (Fig. 6), is distinguished from the above by its more rapid movements, larger size, and longer and rounder body. Its habits and diet are much the same, though they are not found, together.

It is the species most commonly met with in stores of cantharides, which are very subject to attacks of mites. This species, Mr. Murray says, gave rise about 1837 to a good deal of talk among scientific people, as having been supposed to be produced by electricity. There was at that time in the semi-scientific world a vague idea in favor of electricity being the source of many of the phenomena of life. The limits and extent of its power were, of course, even less known than at present, and all sorts of wild experiments were tried. One gentleman set up lines of electrical wires over portions of his estate, with a view of ascertaining whether the plants would not thrive better under what he supposed would be an increased flow of electricity. Others made similar experiments in different directions. One gentleman, Mr. Cross, tried to produce organic beings by the aid of electrical apparatus. His process was to operate on volcanic stone kept moist by a solution of silicate of potash and muriatic acid, constantly subjected to electricity. After carrying this on for some time, he was rewarded by finding some of these mites wandering about his apparatus, and arrived at the conclusion that they had been produced by his electrical batteries. The species, therefore, enjoyed an ephemeral fame as a human creation. It was sent to M. Turpin, in Paris; having but a single dead specimen to work from, he believed it to be a new species,