gall midge

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

• noun Any of numerous small flies of the family Cecidomyiidae, whose larvae cause the formation of galls in plants.

from The Century Dictionary.

• noun A gall-gnat. See Gallicolæ, 2.

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

• noun Any insect of the Cecidomyiidae family, whose larvae damage crops and other plants, creating galls on the stems and other fleshy parts.

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

• noun fragile mosquito-like flies that produce galls on plants