There are hundreds of different species of aphids, some of which attack only one host plant, while others attack numerous hosts. A characteristic common to all species is the presence of two tubes, called cornicles, on the back ends of their bodies. The cornicles secrete defensive substances. In some species they are quite long, while in others they are very short and difficult to see.
Aphids feed in clusters and generally prefer new, succulent shoots or young leaves.
Some species, known as woolly aphids, are covered with white, waxy filaments which they produce from special glands. Aphids have unusual and complex life cycles which allow them to build up tremendous populations in relatively short periods of time. Most species overwinter as fertilized eggs glued to stems or other parts of plants. Nymphs which hatch from these eggs become wingless females known as stem mothers. There are no males present at this time.