Adult females are often characterized by a white, mealy or powdery secretion that covers the body. Species that occur in concealed habitats such as grass sheaths either lack this secretion of have only small amounts of it. Frequently marginal areas of the body have a series of protruding lateral wax filaments. These filaments may be absent, confined to the posterior 1 or 2 abdominal segments, or occur around the entire body perimeter. A filamentous secretion often is produced that encloses the eggs and at least part of the body.
No single character can be used to determine a specimen as a pseudococcid. Mealybugs are a large and diverse group and exceptions occur for every character. There are species without ostioles, cerarii, circuli, trilocular pores, and translucent pores. Although the family is quite distinct, it is best to use a combination of characters for its recognition. Most mealybugs lack concentrated pores near the entrance of the spiracular atrium but species of Antonina, Chaetococcus, Peridiococcus, Sphaerococcus and a few other genera have pores concentrated near the atrium entrance and Syrmococcus species have them embedded in a sclerotized area contiguous with the atrium. Pseudococcidae Cockerell was first used as a family by Lobdell (1930).
Based on an analysis of the host information in the mealybug catalogue by Ben-Dov (1994), mealybugs occur on about 250 families of host plants. The most common host family is Poaceae with 585 species. The Asteraceae is a distant second with 250 species. The top ten most common host families are: Fabaceae 225; Rosaceae 116; Rubiaceae 101; Euphorbiaceae 97; Myrtaceae 94; Labiatae 85; Moraceae 82; Cyperaceae 75. It is interesting that grasses and composites are such important hosts of mealybugs, but are far less common as hosts of armored scales. This might be explained by the tendency for mealybugs to occur on more herbaceous plants and on fewer trees and woody shrubs. There are surprisingly few mealybugs on families such as Salicaceae, Pinaceae, Palmaceae, and Betulaceae.
Mealybugs have 4 female instars and 5 instars in the male. Mealybugs have a diverse array of life history strategies from occurring in grass blade sheaths, to feeding on rootlets to occurring exposed on leaves. Thus any generalized life history will have many exceptions. Many mealybugs overwinter as second instars, although adults, first instars, and eggs also can play this role. Eggs or first instars are laid by the adult female. Eggs are normally laid in an ovisac that can enclose all or part of the body of the female. Most species that lay first instars rather than eggs lack any substantial ovisac. Even though the majority of species have legs in all instars, most mealybugs remain relatively stationary throughout their life; a few species such as some members of the genus Phenacoccus, move to different areas of the host for overwintering, feeding, oviposition, and molting. Most species have 1 or 2 generations a year, although some are reported to have as many as 8 generations in the greenhouse. Both parthenogenetic and sexual species are common.