so the infestation is of something else - they are predators of aphids (and possibly other small plant-feeding creatures). In the left of this photo you can see one with what appears to be a brown aphid in its jaws. It's unusual to see such a cluster of them, in my experience - although if you look at the comment on this one (below), which seems to be the same species (Seven-spotted ladybird), it describes a similarly large group.