Larvae idenfication

I've been searching the Internet for a while looking for guides to identifying ambystomid larvae, and I was wondering if any of you have any references, guides, or tricks for identifying them. I'm mostly concerned with the three species occuring in Wisconsin, (laterale, tigrinum, and maculatum). I'm getting pretty good at IDing eggs, but if I want to look now it'd be easiest if I could tell what they are before they metamorph (and I'd have to keep instead of releasing them). I e-mailed the Wisconsin Department of Natural Resources for a publication, but I'm unable to check my campus e-mail for some reason to check for a reply, so any help in the meanwhile would be appreciated, thanks.

the only reference guide to larvae i can think of off the top of my head (reference as in its a key to identification)is unfortunately the petersons guide for western species...so your out of luck there...im not sure if i'd rely on anything like that being on the web

Thanks, that helps a bit. I knew most of my larvae were maculatum, but lost track of the eggs that were laterale, and recently added a few small wild-born larvae. The biggest question was that I'd found some eggs that I believed to be tigrinum, but she was staying just above 2 inches, same size as my largest maculatum. I knew that tigrinum were larger, but was hoping that I just had large maculatum and a small tigrinum, but she's clearly not anywhere near the min. size range.

Thanks for the help.