Have you ever heard your parents complaining about greenfly on the roses or other plants in your garden? Well, the proper name for greenfly is aphids. They are insects, and can be very harmful to plants if they are not dealt with because they suck out the sap from the stem of the plant and make it grow stunted or deformed. They can also spread plant viruses, in particular one which attacks potato plants. But aphids have an interesting life style. When they have sucked out the sap from the plant, aphids secrete a sweet liquid called honeydew, which ants love. In fact, so found are the ants of this honeydew that they keep herds of aphids near them, and they stroke the aphidsí sides to encourage the to secrete the honeydew. A strange case of dairy farming in the insect world, isnít it?