Pennsylvania Leatherwings are among the most common members of the Soldier Beetle family, They were once classified with the closely-related Lightening beetles and they find it beneficial to mimic LBs because LBs have poisonous blood that oozes from the base of their wing covers. PLWs have their own "super powers" – both the adults and the larvae share the ability to produce "defensive chemicals" via glands in their abdomens.
They're common throughout the East, not limited to Pennsylvania. Leatherwing? Their elytra, the usually hard, front pair of wings that protect the flying wings beneath, are uncharacteristically soft and flexible. Soldier? The soft, cloth-like wing covers of some species sport bright colors/stripes that remind (some) people of soldier's uniforms.
All this information was supplied by master landscape artist and friend, Robyn who identified the beetle for me when our paths crossed as I was taking pictures. I'm not sure what the beetles were doing but the less said, the better.
