In commercial and everyday use, the term weight is usually used to mean mass, and the verb to weigh means to determine the mass of or to have a mass of. Used in this sense, the proper SI unit is the kilogram (kg).
For other uses, see Aphid (disambiguation). Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies, or whiteflies (not to be confused with jumping plant lice or true whiteflies), are small sap-sucking insects, and members of the superfamily Aphidoidea.
Many aphid species prefer the underside of leaves, so turn leaves over when checking for aphids. On trees, clip off leaves from several areas of the tree. Also check for evidence of natural enemies such as lady beetles, lacewings, syrphid fly larvae, and the mummified skins of parasitized aphids.