citrus' little helper

Recently the garden's been overrun by aphids, including on the new growth of my designer twig.  I found heaps of these little critters all over my tree and had a bit of a panic because I'd never seen them before.  They looked kind of like a ladybug only smaller and they had some strange white powder on them.

Thanks to my friends at OzGrow garden forum, I found out it's a yellow-shouldered ladybird, one of the many "good" ladybugs that chows down on aphids.  I've never seen so many ladybugs on one plant, and they sure did a good job - the aphids are gone!  Good thing I checked before I sprayed.