Arachnida
Pronunciation : A*rach"ni*da
Part of Speech : n. pl.
Etymology : [NL., fr. Gr. (Zo?l.)
Definition : Defn: One of the classes of Arthropoda. See Illustration in Appendix.
Note: They have four pairs of legs, no antenn? nor wings, a pair of mandibles, and one pair of maxill? or palpi. The head is usually consolidated with the thorax. The respiration is either by tranche? or by pulmonary sacs, or by both. The class includes three principal orders: Araneina, or spiders; Arthrogastra, including scorpions, etc.; and Acarina, or mites and ticks.
Source : Webster's Unabridged Dictionary, 1913