"Aren't they cute?" is what I said to my friend when we saw scores of these ladybugs on a tree in the province of Vojvodina (VOY-vo-deen-a) north of Belgrade. They are cute and they are ladybugs, but not the domestic kind, as you can see by their variations. They're Asian ladybugs and were imported for use in greenhouses to control aphids, a common pest. These ladybugs have become pests themselves, since they weren't happy being confined just to greenhouses. They apparently threaten the domestic ladybug, they bite (so people claim), and when squashed they release a yellow powder which leaves a stain.
I think they look like bumper cars on this photo.