At first I thought the difference is in the shape of the wings, but I'm finding both rounded and more pointed wing tips for both. The colour could be a clue too but that might not be so reliable.
http://bugguide.net/node/view/...
http://www.butterfliesandmoths...
http://bugguide.net/node/view/...
http://www.butterfliesandmoths...
There is a suggestion the colour of the head is the difference, but that's not certain.
https://www4.uwm.edu/fieldstat...
The mothphotographersgroup shows a pale head in all examples of Hypoprepia fucosa ..
http://mothphotographersgroup....
But, that's not the case for Hypoprepia miniata!
http://mothphotographersgroup....
Bugguide states "H. fucosa (Painted Lichen Moth), forewing has extensive yellow"
http://bugguide.net/node/view/...
Discussion on the topic, look at the reply from maractwin (actually gcwarbler, the poster's name is at the bottom). It seems almost impossible to separate them, often it comes down to the genitalia.
http://www.inaturalist.org/obs...
