LIFE HISTORY. Nearly all mites deposit eggs, frequently of large size. In a few forms the larvae issue from the parent, but in some eases it is rather from the egg within the body of the dead mite. In many cases the hard external skin or chorion of the egg splits into halves and exposes the lining vitelline membrane; this per mits the maturing egg to increase in size, which is then called a `deutovnin."Ihe young larvte on hatching commonly have six legs, but the gall mites have but four. During the nymphal stage the mite feeds until it attains adult size. In many cases the nymph nodts directly into the adult mite, but in several families the nymph often transforms into a creature entirely differ ent from both the nymph and the adult—the hypopial stage or 'llypopus,' long supposed to be a distinct genus of mites. On its ventral or under surface is an area of sueking-disks, by which the Hypopus attaches itself to an insect or small mammal, and is transported to some new and suitable locality, where it falls from its carrier, molts into an oetopod nymph, begins feeding, and in due time becomes an adult mite. The is, therefore, not a parasite, but a commensal, making use of the carrier only for transportation; and in certain gamasids (Ur°, pods I the mite in this migratorial stage is at tached by a thread of hardened excrement to its host.
In some families as the Trombhliidx) the larval and nymphal stages are attached to vari ous insects and feed thereon, while the adult is free. In of the beetle-mites the nymph car ries on its back old molted skins, egg-shells, an'l other diThris. In these mites there is a consid erable resting-period while the nymph is chang ing to the adult, a period when much of the internal anatomy is entirely changed; and it lies been observed that when the adult emerges its legs are not withdrawn front the legs of the nymph. hut from beneath the body. In the bird mites there is a transition-form 'between the nymph and the adult female, known as the nymphal female. The adult male mates with this nymphal form, and when the real adult emerges, an egg, already of considerable size, is seen in her body. Parthenogenesis has been ob served in a number of mites. As a rule, mites
possess no special accessory sexual organs, com parable to those of spiders, but in some male pa wasidg the mandibles carry the globule of sperm cells and insert it in the female vulva. In many species the males have one pair of legs enlarged and modified to act, as (gaspers for hold ing the female. The eggs are usually deposited singly, but many gall-mites and harvest-mites place than in clusters.
Ii.ym•rs. The habits of mites are very diverse, :Most mites ordinarily move quite slowly and de liberately; very few notes are fitted for leaping. The spinning mites or 'little red spiders' (Te iranychus) produce a titre• thread wherever they go, the accumulated threads of many individuals making a NVI1 itiSh nu•sh or web. .More than one half of the knoutt mites are parasitic, at least (luring part of their life. The ticks are well known to infest various mammals, birds, and even snakes and turtles. They have mouth-parts especially titled for cutting into the skin of the host and sucking up the blood. (See Tick.) One group of the gamasids is parasitic on bats, birds, and small mammals. The bird-mites live upon the skin and feathers of birds, but as they feed upon epidermal scales and loose hits of feathers, they do not. injure their hosts, but are rather of service in keeping the skin and feath ers clean. The itch-notes burrow within the skin of man •tnd other mammals. Other species live in the cellular tissue of birds. A few occur in the tracheal passages of seals. and one has been found living in the lung of a monkey. species feed on living plants, and the gall-mites produce deformations on the leaves and twigs of plants. Since these gall-mites are invisible to the unaided eye, the deformations were formerly supposed to be fungi. luny of the beetle-mites feed on fungi, lichens, and other low veget:it ion. A large number of mites are predaeeous and :Mark other mites and small insects. There is a large family, the watu•ntites, living in fresh water, sometimes as commensals within the gills of bivalve molhisk,; another group lives in the (wean, even at a considerable depth. In recent years investigators have found a number of mites associated with ants.