The curious Beetle-parasites attached to their victim by a thread belong to the genus Uropoda of the Uropodinae. The connecting filament, which the Mite can sever at will, for a long time puzzled observers. It was variously construed as a silken cord of attachment, and as a sort of umbilical cord, through which the Mite drew nourishment from the Beetle. On more careful investigation it proved to be connected with the anus of the Mite, and to consist of its consolidated excrement.
The Dermanyssinae are all parasitic on warm-blooded animals, principally birds and bats. Dermanyssus avium is the common parasite infesting fowls and cage-birds.
Sub-Order 4. Heterostigmata.
Fam. Tarsonemidae.—This is the sole family of the sub-order. It comprises a number of minute vegetable-feeding Mites which have been little studied, though they are probably the cause of considerable injury to the leaves and buds of plants.
Sub-Order 5. Prostigmata.
In these Mites the stigmata are situated anteriorly, in the rostrum or the thorax. In the Water-mites the tracheae have atrophied, but these creatures are clearly Trombidiidae which have taken to an aquatic life.
Fig. [246].—Bdella lignicola, x about 50. (After Canestrini.)
Fam. 1. Bdellidae.—The Bdellidae are sometimes known as the “Snouted Mites” on account of the very prominent forwardly-directed “capitulum” or false head. They have chelate chelicerae and tactile palps, which are often “elbowed,” like the antennae of weevils. Eyes may be present or absent. They are usually of a bright red colour, and are free-living and predaceous, though in their larval stages they may often be found attached to the limbs of insects and spiders.
The minute active scarlet Mites of the genus Eupodes and its allies perhaps come within this family. Their legs are six-jointed.