The Collaborative International Dictionary of English v.0.48:

Negro \Ne"gro\, a.
   Of or pertaining to negroes; black.
   [1913 Webster]

   Negro bug (Zool.), a minute black bug common on the
      raspberry and blackberry. It produces a very disagreeable
      flavor.

   negro corn, the Indian millet or durra; -- so called in the
      West Indies. See Durra. --McElrath.

   Negro fly (Zool.), a black dipterous fly (Psila rosae)
      which, in the larval state, is injurious to carrots; --
      called also carrot fly.

   Negro head (Com.), Cavendish tobacco. [Cant] --McElrath.

   Negro monkey (Zool.), the moor monkey.
      [1913 Webster]