This beetle is a Strangalia luteicornis. It was one of many beetles of this species crawling on the limbs of a flowering winterberry bush. Strangalia luteicornis is a common eastern beetle species, with a distinctive shape and markings. Like other members of its genus, adults of this species are often found around flowers, where they feed on nectar.
Some of these beetles were piled in a clump, as if they were struggling with each other.
Others were mating.
In some cases, more than two were involved in a mating session. I saw a few triple-decker mating groups. It is amazing that they can keep their balance in a position like that.
In the photo above, three are piled up, and a fourth looks like it wants to join. Three seemed to be the maximum number that would work, though. When more beetles got involved, the stack would usually fall apart.