This family contains around 200 species of aphids which often have a flat and round shape in the unwinged adult stage with short legs and antennae which do not protrude under the body. Several species are important agricultural pests and often restricted to a certain group of host plants, e.g. Cerataphis brasiliensis infests palm trees.
Hormaphididae are often heteroecious and the sexual and asexual forms develop on different host plants. Some species produce galls during their sexual stage. The family is sometimes regarded as a subfamily (Hormaphidinae) of the Aphididae.
The following genera and individual species are currently entered under Adelgidae: