Anita, that's a Monarch caterpillar and nymphs of Milkweed Bugs. The MBs are primarily seed feeders, as you can see.

I smash those milkweed bug nymphs - and the adults as well. They really lay waste to my milkweed plants. Aren't they sucking insects, like aphids?

Thank you. This is my second year with butterfly weed and my first sighting of monarch cats. I’m pretty excited about it!

Yes, Carol. They are "true bugs".

Oh they'll wreck leaves alright. Diligence required;
smash them, spare not a one.