Ladybugs are small oval beetles, red or orange with small black markings. The length depends on the species 4-6mm. They are a beneficial insect for every garden.
Lady Bugs (left)-Odonals Nursuries, Ladybugs (right)-Charles W. Melton
There are more than 400 different species found worldwide. They have wings and can fly great distances. The larvae are elongated and are very small. They resemble small black alligators. they have red or orange markings on their bodies.
Larvae (left)-Odonals Nursuries, Ladybug eating aphid
Lady bugs overwinter as adults in protected areas around the home and garden. I once found a bunch right at the door of the root cellar. In the spring they fly looking for plants to deposit their eggs on. The eggs hatch and go through several larval stages. While in this stage they feed on aphids. They will pupate in late summer on the leaves or stems of host plants.
Lady Bug egg mass (keft)-R. Bessin, University of Kentucky Entomology, Lifecycle-Kunafin
They are primary aphid eaters but they also eat mites, eggs and other small plant sucking insects. If aphids are not in your garden lady bugs will also eat eggs of many moths and other harmful insects. Lady bugs travel wide areas so they also help in the pollination process. You can buy these insects at many garden shops. Before you do this however, I would recommend you make sure they are NATIVE to your area. Sometimes unnative insects will attack native species. Plenty of aphids is the key to keeping lady bugs in your garden. They can eat as many as 50 per day and have a tendency to leave gardens if they run out of this main food source. They are definitely an asset in your greenhouse where they will stay and keep down whitefly populations as well.
This is the Asian ladybug (left)-Suite101.com, group in a kitchen-R.A. Casagrande
These are not native to North America and they can pose a problem to some homeowners. In the fall around October they have a tendancy to come into your home. Once in they emit phermones that attrack other Asian ladybugs. Soon your house could become overcrowed by them. The difference between native and nonnative is the white letter W or M in the middle of their back. Keep in mind that even these ladybugs are still somewhat beneficial as the do still eat aphids and other insects. Read this article Good Bugs Gone Bad.