This was one of several beetles on the milkweed leaf, and after I took this photo, it proceeded to feed on the aphids. Asian Lady Beetles were imported for just this purpose, and were sold in garden centres by the bagful. That has now stopped as far as I know, because they have spread widely, but they still spend a lot of time consuming aphids as well as other insects. Both the adults and the larvae of this species feed on aphids.