black fly

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various small, dark-colored biting flies of the family Simuliidae, the larvae of which attach to rocks in streams and other flowing waters.

from The Century Dictionary.

• noun A small dipterous insect, Simulium molestum, with a black body and transparent wings, abounding in mountainous and wooded parts of New York, New England, and northward, and exceedingly annoying to both man and beast. It is closely related to the buffalo-gnat. See Simulium.
• noun The bean-plant louse, Aphis fabæ.

from the GNU version of the Collaborative International Dictionary of English.

• (Zoöl.) 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 larvæ are aquatic. It sucks the blood of birds as well as humans and other mammals.
• A black plant louse, as the bean aphis (Aphis fabæ), which infests e. g. beans and sugar beets; -- called also bean aphid.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Alternative spelling of blackfly.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun small blackish stout-bodied biting fly having aquatic larvae; sucks the blood of birds as well as humans and other mammals
• noun small blackish stout-bodied biting fly having aquatic larvae; sucks the blood of birds as well as humans and other mammals
• noun blackish aphid that infests e.g. beans and sugar beets