Arachnida
the class of animals which contains spiders, scorpions, and mites. It is placed between the crustacea on the one hand, and the insecta on the other. The highest crustacea have 10 feet, the arachnida 8, and the insecta 6.
The arachnida are wingless, have no antennæ, breathe by means of tracheal tubes or pulmonary sacs performing the function of lungs. As a rule, they have several simple eyes. They have no proper metamorphosis. They live in a pred- ARAGON atory manner. Huxley separates the arachnida into six orders: (1) Arthrogastra, including scorpio, chelifer, phryaraneina, or spiders; (3) acarina, or nus, phalangium, galeodes, etc.; (2) mites and ticks; (4) fresh-water arctisca or tardigrada, called water-bears; (5) pycnogonida (marine animals); and (6) pentastomida (parasites).