An old work (1918) by J. M. Aldrich, but perhaps still useful in trying to ID some Fucellia to species, due its detailed descriptions and helpful line drawings.

If for some reason the link below fails, a stripped-down "full-text" version (i.e. without the nice original page formatting and figures) can be viewed here. (Note: Use the "Find" command in your browser with "The Kelp-Flies of North America"...or you'll have to scroll a long ways to get to the paper!) That said, for most purposes the link below is far better way to go.