This interesting lep larva left a very distinctive sign on its host plant. The sign I came across: goldenrod stem "stumps" maybe six inches tall. Here is one such "stump," with dormant shoot attached, after I cut it off at ground level and brought it inside:
From a distance, when it was still in the ground, it might appear as if this were simply the bottom part of a stem left over after the majority of the plant had broken off on its own accord, maybe on a blustery midwinter day. But a closer look revealed that something inside the stem had deliberately created a neat beveled cut all the way around the stem, causing it to break off -- and then sealed the cut with compacted frass:
I found three such stumps, all cut in exactly the same way, within a one-square-meter area on a roadside embankment. The above thumbnails both link to pictures of one of those stumps, which I collected by cutting it off at ground level. Nothing was inside of it, but it had been hollowed out all the way to ground level and below; I didn't check to see if there was anything in the belowground portion of the plant. Fortunately, for another such stump I cut off at ground level, I did check, and there was a sizable lep larva in the root of the plant, just below ground level. That larva is shown in this series; also shown (see last photo) is the root it came from, cut open to reveal the tunnel it dwelled inside (which was continuous with the tunnel in the stump leading up to the beveled cut).
I saved the root piece shown in the last photo of this series and was able to get it to sprout; it is healthy and growing. I hope to keep it alive until it flowers so I can identify it more certainly, but for now all I can say is that it's a Solidago
5/19/17 Adult emerges (see last photo in this series)
5/7 - 5/8/17 Adult plume moths emerge from similar goldenrod stumps collected in Vernon Co., WI: