Tetraopes tetrophthalmus (Coleoptera: Polyphaga: Chrysomeloidea: Cerambycidae: Lamiinae: Tetraopini). Sky Meadows State Park, Fauquier County, VA. 04 July 2006
Type "beetle red milkweed" into BugGuide.net and you'll find that this is called, strangely enough, a Red Milkweed Beetle. More info: www.texasento.net/tetrophthalmus.htm
Two milkweed beetles were apparently mating on the milkweed.