Ladybugs aren't true "bugs," they are beetles of the Coccinellidae family. The largest population of ladybugs in the United States now is actually the Asian lady beetle (Harmonia axyridis), introduced by the Department of Agriculture to control aphids in the early 1900's. Because they are have more voracious appetites, they quickly outcompeted many native species.
For about $10, you can get approximately 1000 ladybugs from your local nursery, or online through Amazon or Gardeners.com. Ladybugs may be stored in the refrigerator for up to 2-3 months depending on the time of year, where they live off body fat and appear almost catatonic. New ladybugs birth at around June-July, these can be stored longer; whereas ladybugs bought in March-April should be used sooner since they are approaching the end of their lifespan.
For best results, mist the garden areas slightly with dechlorinated water, then release the ladybugs at dusk. If your garden is relatively pesticide-free and pest-heavy, the little beetles will drink and eat throughout the night. A single lady beetle may consume upwards to 5,000 aphids in a single evening. In the morning may will fly away, but a few will stick around to breed and populate your garden.
Now, control your urge to spray pesticides all over the garden. If you still encounter large outbreaks that the ladybug population can't presently deal with, spot treat the location with some diluted dish soap, or manually remove/pinch off the affected areas. Ladybugs are very sensitive to any chemicals (including neem oil).
Want to share your experience with ladybugs? Have other insect carnivore or sustainable pest control recommendations? Head over to our forums.