These awful-looking little mites are said to have two large eyes, and legs of five segments and of equal length. Their colour is greenish to brownish yellow. Undoubtedly there are many mites which live as endo-parasites; certain members of the group Analgesinae, such as Laminosioptes gallinarum, live in the intramuscular and subcutaneous tissue of fowls, and Cytoleichus sarcoptioides in their air-sacs. I have myself found one of these species in the pigeon, so that it is by no means beyond the bounds of human possibility that Nephrophages sanguinarius really lived in the tissues of the Japanese. Very strange things live in the tissues of some Japanese.
CHAPTER IX
TICKS
A waterleche or a tyke hath neuer ynow, tyl it brestyth.
(Jacob’s Well, 1440.)
Ticks are mites ‘writ large,’ and until about the beginning of this century they were regarded with what one might call mild disgust and regret. Now, however, that they have been proved to play a part—and a very important part—in the dissemination of disease, we have come to regard them, as Calverley said we should regard the Decalogue, ‘with feelings of reverence mingled with awe.’
The body of a tick is covered with a tough, smooth or crinkled skin, capable almost of any amount of extension. Until they have fed they are flattened in shape, but after a meal of blood they very soon lose the outlines of a Don Quixote and attain those of a Sancho Panza. In the adult, the legs are eight in number and have six joints ending in two claws and sometimes in suckers. Some have eyes and some have no eyes.
Fig. 41.—Evolution of Argas persicus. 1, the egg; 2, the six-legged larva; 3, the same gorged; 4, an unfed nymph; 5, nymph gorged. (After Brumpt.)
The most formidable part of their armour is, however, the mouth-parts, consisting of the tactile pedipalps, and the piercing-probe which they stick into our bodies. This probe consists of a dorsal membranous sheath and a ventral hypostome armed with recurved teeth, forming together a tube within which play two cutting and tearing chelicerae. When these have cut a way into the flesh they are withdrawn, and the tube is inserted into the wound and blood is pumped up it by the sucking-pharynx. It is the teeth on the hypostome, and not the chelicerae, which anchor the ticks to their prey.