The Collaborative International Dictionary of English v.0.48:

Macaca \Macaca\ prop. n.
   A genus of macaques including the rhesus monkey (Macaca
   mulatta), much used in laboratory biomedical research.
   Formerly called Macacus.

   Syn: genus Macaca.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Macaca mulatta \Macaca mulatta\ n.
   The rhesus monkey of South Asia; used in medical research.

   Syn: rhesus, rhesus monkey.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Macaque \Ma`caque"\, n. [F. See Macacus.] (Zool.)
   Any one of several species of short-tailed monkeys of the
   genus Macaca (formerly Macacus), found in rocky regions
   of Asia and Africa; as, Macaca maurus, the moor macaque of
   the East Indies.

   Note: Macaca mulatta is the Rhesus monkey, much used in
         biomedical research, and namesake of the Rh factor used
         in blood typing (due to discovery of that factor in the
         Rhesus monkey).
         [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

Macaca mulatta
    n 1: of southern Asia; used in medical research [syn: rhesus,
         rhesus monkey, Macaca mulatta]