In our area there are two Marathyssa species, Dark (Marathyssa inficita) and Light (Marathyssa basalis). I encountered my first Marathyssa last year, but I didn't photograph both species and get their proper identifications clear in my mind until this year. The one on the left is Dark Marathyssa and the one on the right is Light Marathyssa. They are modest-sized moths that fold their forewings when at rest. Sitting on a moth sheet or the side of a building they seem fairly obvious. Think about trying to find one sitting on a twig or a section of rough bark. Tough!