With Drosophila melanogaster, wild type usually means the standard version of the famous laboratory population used in the T.H. Morgan laboratory, and since used around the world. This was, of course, only a small sample of the natural populations.
Actually, we propbably know more about Drosophila pseudoobscura in the wild than Drosophila melanogaster, because of a huge series of studies done by Theodosius Dobzhansky and his colleagues after World War II.
- Futuyma D.J. Evolution. Sinauer, Sunderland, Massachusetts. p556
- Lewontin R.C; Moore J.A; Provine W.B. & Wallace B. 2003. Dobzhansky's Genetics of natural populations, I–XLIII. New York: Columbia University Press.