Mite-galls, or acarocecidia, are abnormal growths of the leaves of plants, produced by microscopic Acaridea of the genus Phytoptus (gall-mites), and consist of little tufts of hairs, or of thickened portions of the leaves, usually most hypertrophied on the upper surface, so that the lower is drawn up into the interior, producing a bursiform cavity.
A great variety of deformations and growths produced by insects and mites as well as by fungi have been described.
Zukal has considered that the lichen acids protect the lichen from the attacks of animals; the experiments of Zopf, however, have cast doubt on this; certainly lichens containing very bitter acids are eaten by mites though some of the acids appear to be poisonous to frogs.
While the majority of the Thysanoptera are thus vegetarian in their diet, and are frequently injurious in farm and garden, some species, at least occasionally, adopt a predaceous habit, killing aphids and small mites (so-called "red-spiders") and sucking their juices.
It is possibly for the purpose of feeding on parasitic mites that book-scorpions lodge themselves beneath the wing-cases of large tropical beetles; and the same explanation, in default of a better, may be extended to their well-known and oft-recorded habit of seizing hold of the legs of horse-flies or other two-winged insects.
The same naturalist describes the association with Lasius of small mites (Antennophorus) which are carried about by the worker ants, one of which may have a mite beneath her mouth, and another on either side of her abdomen.
On patting their carrier or some passing ant, the mites are supplied with food, no service being rendered by them in return for the ants' care.
Ants invite one another to work, or ask for food from one another, by means of pats with the feelers; and they respond to the solicitations of their guest-beetles or mites, who ask for food by patting the ants with their feet.
It is probably owing to the possession of such glands and the varied purposes for which the silk is used that spiders as a group far surpass the other orders of Arachnida, with the possible exception of the Acari (mites and ticks), in diversity of form and of size, in numbers of genera and species, in extent of geographical distribution, and in adaptation to varied habitats.
Locusts, green-fly, leaf-bugs, blister mites, and various other pests also damage cotton, in a similar way to that in which they injure other crops.
They are then dried and put up for preservation in glass-stoppered bottles; and they require to be very carefully guarded against mites and various other minute insects, to the attacks of which they are peculiarly liable.
Apec vr7, a spider) to a class which he instituted for the reception of the spiders, scorpions and mites, previously classified by Linnaeus in the order Aptera of his great group Insecta.