First picture, the nymphs (youngsters) of milkweed bugs.

The 2nd photo, aphids.

And whenever you grow milkweed, you should plan to deal with both.

You can blast the aphids off with harsh spraying with the hose. As much as I hate those blasted aphids, I rear monarchs from the egg stage and would never consider getting rid of my milkweeds. One year, I had such a severe infestation that I cut it all back, before my knowledge of caterpillars & ladybugs. It was going dormant anyway. Keep your eye out for ladybug larvae too; they'll have a feast!
Here's one of my pics from 2006:
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