Such a fanciful common name has been applied to this little moth! It stems from the fact that the larval stage of this moth has a horn-like protrusion from its body. I only managed to get one decent photograph of the moth, but it certainly was sufficient to identify it.
What struck me as unusual about this moth was the angle at which it held its wings while sitting on my wall. It has a very striking angle, as if it's preparing for take-off!
I snapped this one on August 12, and that's normal for this moth - it does appear later in the season.
The larvae feed on a wide range of plants and trees, including alder, apple, aspen, birch, elm, hawthorn, hickory and willow. There is plenty of alder on my farm, as well as aspen, apple and birch, not to mention elm. No wonder it decided my place was a good spot to hang out!