A division of Arachnoidea, including the daddy longlegs or harvestman (Phalangium) and many similar kinds. They have long, slender, many-jointed legs; usually a rounded, segmented abdomen; and chelate jaws. They breathe by tracheæ. Called also Phalangides, Phalangidea, Phalangiida, and Opilionea.  [1913 Webster]