The Collaborative International Dictionary of English v.0.48:

Praying \Pray"ing\,
   a. & n. from Pray, v.
   [1913 Webster]

   Praying insect, Praying locust, or Praying mantis
      (Zool.), a mantis, especially Mantis religiosa. See
      Mantis.

   Praying machine, or Praying wheel, a wheel on which
      prayers are pasted by Buddhist priests, who then put the
      wheel in rapid revolution. Each turn in supposed to have
      the efficacy of an oral repetition of all the prayers on
      the wheel. Sometimes it is moved by a stream.
      [1913 Webster]

WordNet (r) 3.0 (2006):

praying mantis
    n 1: the common mantis [syn: praying mantis, praying mantid,
         Mantis religioso]