Do the caterpillars add more coloring as they age? I found this one quickly marching across my lawn last year, none were seen in the garden or elsewhere. It does have a spike horn, so at least must be related. It was all lime green, some pale yellow barely seen striping along the segments, but none of the dots or dramatic polka dots that are shown in the ID pictures. The pics I took showing more underside were kind of blurry, but there were no dots.
So which kind was this? Have never seen one up here before.