The Collaborative International Dictionary of English v.0.48:

black fly \black fly\, blackfly \blackfly\, (Zool.)
   1. In the United States, a small, venomous, two-winged fly of
      the genus Simulium of several species, exceedingly
      abundant and troublesome in the northern forests; --
      called also buffalo gnat. The larv[ae] are aquatic. It
      sucks the blood of birds as well as humans and other
      mammals.
      [WordNet 1.5 + WordNet 1.5]

   2. A black plant louse, as the bean aphis (Aphis fab[ae]),
      which infests e. g. beans and sugar beets; -- called also
      bean aphid.
      [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Buffalo \Buf"fa*lo\, n.; pl. Buffaloes. [Sp. bufalo (cf. It.
   bufalo, F. buffle), fr. L. bubalus, bufalus, a kind of
   African stag or gazelle; also, the buffalo or wild ox, fr.
   Gr. ? buffalo, prob. fr. ? ox. See Cow the animal, and cf.
   Buff the color, and Bubale.]
   1. (Zool.) A species of the genus Bos or Bubalus
      (Bubalus bubalus), originally from India, but now found
      in most of the warmer countries of the eastern continent.
      It is larger and less docile than the common ox, and is
      fond of marshy places and rivers.
      [1913 Webster]

   2. (Zool.) A very large and savage species of the same genus
      (Syncerus Caffer syn. Bubalus Caffer) found in South
      Africa; -- called also Cape buffalo.
      [1913 Webster]

   3. (Zool.) Any species of wild ox.
      [1913 Webster]

   4. (Zool.) The bison of North America.
      [1913 Webster]

   5. A buffalo robe. See Buffalo robe, below.
      [1913 Webster]

   6. (Zool.) The buffalo fish. See Buffalofish, below.
      [1913 Webster]

   Buffalo berry (Bot.), a shrub of the Upper Missouri
      (Sherherdia argentea) with acid edible red berries.

   Buffalo bird (Zool.), an African bird of the genus
      Buphaga, of two species. These birds perch upon
      buffaloes and cattle, in search of parasites.

   Buffalo bug, the carpet beetle. See under Carpet.

   Buffalo chips, dry dung of the buffalo, or bison, used for
      fuel. [U.S.]

   Buffalo clover (Bot.), a kind of clover (Trifolium
      reflexum and Trifoliumsoloniferum) found in the ancient
      grazing grounds of the American bison.

   Buffalo cod (Zool.), a large, edible, marine fish
      (Ophiodon elongatus) of the northern Pacific coast; --
      called also blue cod, and cultus cod.

   Buffalo fly, or Buffalo gnat (Zool.), a small dipterous
      insect of the genus Simulium, allied to the black fly of
      the North. It is often extremely abundant in the lower
      part of the Mississippi valley and does great injury to
      domestic animals, often killing large numbers of cattle
      and horses. In Europe the Columbatz fly is a species with
      similar habits.

   Buffalo grass (Bot.), a species of short, sweet grass
      (Buchlo["e] dactyloides), from two to four inches high,
      covering the prairies on which the buffaloes, or bisons,
      feed. [U.S.]

   Buffalo nut (Bot.), the oily and drupelike fruit of an
      American shrub (Pyrularia oleifera); also, the shrub
      itself; oilnut.

   Buffalo robe, the skin of the bison of North America,
      prepared with the hair on; -- much used as a lap robe in
      sleighs.
      [1913 Webster] buffalofish

WordNet (r) 3.0 (2006):

buffalo gnat
    n 1: small blackish stout-bodied biting fly having aquatic
         larvae; sucks the blood of birds as well as humans and
         other mammals [syn: blackfly, black fly, buffalo
         gnat]