[医] 蛛形纲

[ noun ]
a large class of arthropods including spiders and ticks and scorpions and daddy longlegs; have four pairs of walking legs and no wings
<noun.animal>

Arachnida \A*rach"ni*da\, n. pl. [NL., fr. Gr. ? spider.]
(Zo["o]l.)
One of the classes of Arthropoda. See Illustration in
Appendix.

Note: They have four pairs of legs, no antenn[ae] nor wings,
a pair of mandibles, and one pair of maxill[ae] or
palpi. The head is usually consolidated with the
thorax. The respiration is either by tranche[ae] 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.