We didn't observe this on a milkweed but we found Asclepias asperula and (probably) A. viridiflora in this prairie.
Eastern Milkweed Beetle on Common Milkweed
Red Milkweed Beetle
sky island habitat in the Davis Mountains - Elev. 6000 - Cavalry Campground
Specimen collected and field curated by Dr. Will Godwin (wgodwin)
Identifications, data logging and data labels by Robert J. Nuelle, Jr. (rjnjr)