A genus of very large hairy spiders having four lungs and
   only four spinnerets. They do not spin webs, but usually construct
   tubes in the earth, which are often furnished with a trapdoor. The
   South American bird spider (Mygale avicularia), and the crab spider, or
   matoutou (M. cancerides) are among the largest species. Some of the
   species are erroneously called tarantulas, as the Texas tarantula (M.
   Hentzii).