It looks most like the Erynnis baptisiae to me. It lacks the cell spot that the Juvenal's and Horace's have, yet it has the same coloration. I'm including a link to a picture of a Wild Indigo Duskywing that I raised last year. Your picture looks very much like this one.

Sandy

Here is a link that might be useful: Newly eclosed Wild Indigo Duskywing

Thanks Sandy! I'll have to keep a closer look on my Wild Indigo around here.

E. baptisiae is my first choice also. However, I'm open to E. persius because of the golden spots on the underside hindwing submargin. The Persius is a less common species, so I'm hesitant to mention it.

I wonder whether there's a local expert who might shed some light?

Whatever, it's a male. The butterfliesandmoths.org species descriptions for both species say, "Male has a costal fold containing yellow scent scales." That sounds like the yellow lines I see on your picture above.

Check out the pics below just for their sheer coolness.

Jeff

Here is a link that might be useful: Persius Duskywing

Jeff, Those pictures were amazing. I did some poking around on the internet about E. persius, and of the ways to differentiate it from E. baptisia is that the spots on the edge of the forewings line up straight whereas with E. baptisia those spots are a bit jumbled up.

I sent pics to the NH person on butterfliesandmoths,org and to the Non-Game Division of NH Wildlife. Hopefully I'll hear from someone.