help distinguishing the 3?

This was what I found for the White fringed larva:
http://www.forestryimages.org/images/768x512/1178053.jpg
If this is correct it probably isn't that one?

I doubt it, there aren't too many great references for distinguishing caterpillars. The Wagner book said that the three species I listed above can't really be definitively separated as larvae, since they look so similar, and have overlapping range and feeding preferences. It did say that one species (Red-fringed emerald, N. bistraria)had somewhat longer "wings" on its back, but since we don't have the others to compare to, that's not much use.

If you find another one, definitely try again to rear it out to adult. All you need is a big bag or jar with a whole bunch of the leaves it was eating when you found it. Dump out the frass (poop) every day or so, and be patient.

I'd say to post any alternate photos you took anyway, it might help.

but they always hatch into Tachinid flies >_>. Not one of my 11 Virginia tiger moth larvae survived parasites like these.

Several of my fellow grad students study caterpillar-parasitoid interactions, and would consider that result to be a huge success!

If it happens again, you should post pictures of the fly! Tachinids are generally understudied, according to the one Tachinid expert I know (though he is clearly biased!).

since the one day I forget to check they have hatched and then when I do notice they die....I'll post them later.