Page:Popular Science Monthly Volume 14.djvu/522

506 tropics, and these exotic tick-mites are not infrequently imported on plants, and in the moss and sphagnum which horticulturists use in packing their wares. The habits of this group are somewhat anomalous; at first they are unquestionably herbivorous, but they greedily avail themselves of every opportunity of sucking blood instead of sap. No special adaptation is needed for this, as the sucking-apparatus is suited to both the liquid blood and the juice of plants, and is similar to that of all suctorial insects, which some use on plants, some on animals, and some on both. Of the immense swarms of ticks, gnats, mosquitoes, bed-bugs, etc., the majority probably never taste animal food at all, although so greedy for it when it comes in their way.

The sub-family, Acaridæ, is divided into two sections: the cheese-mites and their allies, and the itch-mites with their relatives. The first section produces a number of vegetable-feeders; several species are found on the scales of some species of Liliaceæ, principally hyacinths, and on dahlia-roots, cyclamen, potatoes, mushrooms, etc.; these occasionally cause itching and irritation to those handling them. The smallest species of this group, Tyroglyphus entomophagus, is a pest too well known to entomologists, upon whose collections it preys. It lives chiefly in the inside of the insects which it attacks, gnawing the soft parts of their bodies, and destroying the ligaments which hold the articulations together, allowing them to fall apart.

Edible mushrooms, especially the cultivated sorts, are often attacked by a moist black rot, which, until lately, has been regarded as spontaneous. But it has been shown that it is caused, or at least aided, by a species of mite remarkable for fecundity. The activity of their agency in this decomposition is shown by the fact that mushrooms on which they have been placed become, in forty-eight hours, a black, putrescent mass, on which myriads of these creatures swarm; while other mushrooms subjected to the same conditions, except the inoculation, dry up, and take from eight days to a fortnight to decompose. The presence of mites in great numbers on some of the common articles of food is well known. These are chiefly the cheese-mites, which are characterized by a soft, smooth, fleshy, whitish body, with generally a single claw, surrounded by a vesicle or fine sucker, like a sieve. T. siro (Fig. 5) is the principal mite which commits ravages upon cheese, living upon all kinds when a little decayed, and especially the harder parts. They hibernate during winter, crowded in heaps in chinks and hollows in the cheese; but with warm weather their activity begins, and they gnaw away, reducing the cheese to powder. This powder is composed of excrement in little grayish balls, eggs, egg-shells, larvae, cast skins, perfect mites, fragments of cheese, and numerous spores of microscopic fungi. A mite-tainted cheese is not objected to by epicures, and the creatures are sometimes introduced to give a premature ripeness; but, if left to work unchecked, they will spoil a cheese very soon.