Answer: the much-loved ladybug. Otherwise known as ladybird, or lady beetle. Or lady cow. Or golden knop, or freyjuhena, or bishy-bishy-barnabee. It depends on where you're from and whom you've named it after. The Norse goddess Freyja? Saint Barnabas? If you opt for "ladybug," you're alluding to "Our Lady" Mary, whose red cloak and seven joys and sorrows correspond to the bug's red shell and seven spots. (But you have to admit, bishy-bishy-barnabee has a nice ring to it.)
Anyway, not all ladybugs are seven-spotted, and not all are red. There are something like 500 different species, some yellow, some grey, others brown or even pink; and each has its specific number of spots. You might have heard you can tell the ladybug's age by counting them, but that's not true. Spots fade with age, but the number stays the same.
So, how do you get ladybugs to live in your garden? Buy some wild-caught from your local nursery. (Farm-raised ladies won't survive in the wild.) Add a little water to their bag and let them rest in your crisper drawer for a few hours. Meanwhile, water your garden well. At dusk, release the ladybugs. If you have an aphid-infested plant, release them right there.
Oh, and by all means, don't crush the larvae! (Check the photo so you know what a lady baby looks like.)
All Seasons Plants is a wholesale broker, but they also sell retail (they exhibited at Yard, Garden & Patio Show and had some beautiful purple-flowering daphne for sale). Their Web site offers good plant information and you can search on a the plant characteristics of interest to you, e.g., bloom time, sun exposure, foliage color, etc.