This is a Blackened Milkweed Beetle (
Tetraopes melanurus), a new species for me. Like Red Milkweed Beetle (also a member of genus
Tetraopes), it feeds on milkweeds, but it favors butterfly weed (
Asclepias tuberosa) rather than common milkweed (
Asclepias syriaca).
The bright red color and black heart shape on its elytra is distinctive.