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.
Note: They have mandibles, modified a poison fa?gs, leglike
palpi, simple eyes, abdomen without segments, and
spinnerets for spinning a web. They breathe by
pulmonary sacs and trache[ae] in the abdomen. See
Illustration in Appendix.