At first glance I almost dismissed this Lesser Swallow Prominent (Pheosia gnoma) as a Swallow Prominent. It was comfortably asleep on the door of the cage so I set the it down while I checked the moth trap. It wasn't until after I was done collecting all of the moths that I realized that it was actually a Lesser Swallow Prominent. The white wedge- or triangle-shaped dash at the top of the wing is the most definite way of telling the two apart, and both receive their genus name after pheos 'a prickly plant, a spine' describing this mark. The Lesser Swallow Prominent receives a double-mention with gnoma 'a mark.'
Lesser Swallow Prominent (Pheosia gnoma)
If you want to see if you can spot the difference, check out the Swallow Prominent in a post by Helen Levins '19 June 2012 - One with the Wood.'