Source : Webster's Revised Unabridged Dictionary (1913)

Leptus \Lep"tus\ (l[e^]p"t[u^]s), n. [NL., from Gr. lepto`s
   thin, small.] (Zo["o]l.)
   The six-legged young, or larva, of certain mites; --
   sometimes used as a generic name. See {Harvest mite}, under
   {Harvest}.