The Collaborative International Dictionary of English v.0.48:

Daddy longlegs \Dad"dy long"legs`\
   1. (Zool.) An arachnidan of the genus Phalangium, and
      allied genera, having a small body and four pairs of long
      legs; -- called also harvestman, carter, and
      grandfather longlegs.
      [1913 Webster]

   2. (Zool.) A name applied to many species of dipterous
      insects of the genus Tipula, and allied genera, with
      slender bodies, and very long, slender legs; the crane
      fly; -- called also father longlegs.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Father longlegs \Fa"ther long"legs`\ (Zool.)
   See Daddy longlegs, 2.
   [1913 Webster]