There are two species of moth that commonly mine grape leaves (Vitis spp.) where I live (Pennsylvania), and I think I’ve figured out how to distinguish them. I’m sharing here just in case somebody might be in need of tips.
The one I most commonly see is the grape leaf miner, Phyllocnistis vitifoliella. It has a very prominent, dark frass line in the center of its mine path, and the epidermis is visibly pushed up by the larva. Further images of the mine (and of the adult) can be found on the relevant BugGuide.net page.
Less commonly found, at least in my immediate area, is the American grape leaf miner, Phyllocnistis vitegenella. Unlike the previous species, there’s no visible frass line (the frass is dark and diffusely deposited, I gather), and the path looks more like the glossy residue left by a slug. A further difference is that late-instar P. vitegenella induce leaf margins to curl slightly prior to pupation. You can see that curling on the upper right part of the leaf in the photograph. BugGuide.net has more mine photographs. Photographs of the adults are here (auf Deutsch).
There are reports of a third species in Pennsylvania (and Kentucky), Antispila viticordifoliella, but I haven’t encountered it. So here’s a link to it’s Wikipedia page, with image from that page. Apparently the frass is collected in irregular lines or big clumps. There’s also A. oinophylla, but apparently it hasn’t been found in Pennsylvania (yet?).
If I’ve made any errors in the above, let me know.