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).