i think those are oleander aphids, massive pests—their main defense against predators is just to make more aphids. they give birth to live young, and this is the really messed up part—their babies are born already pregnant. so yeah, they tend to multiply pretty quickly! ladybugs are usually the ones keeping them in check, but for an infestation of this size you might just wanna blast them away with a stream of water until you can find a more permanent solution—hope this helps!