Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
The Plant-Feeding Gall Midges of North America
By Raymond J. Gagné
Cornell University Press, 1989
ISBN: 0-8014-1918-2
Cite: 214632 with citation markup [cite:214632]
If you've gotten as far as figuring out that your gall was made by a midge (Cecidomyiidae), you should be able to figure out the species from this book's illustrations and keys.

Links to review of and species descriptions from book