Margarodidae
Taxonomic placing: Insecta, Hemimetabola, Hemiptera, Sternorrhyncha, Coccomorpha, Coccoidea.
(Several genera, like Icerya, that were formerly accomodated in this family, were transferred to the family Monophlebidae).
Common name: Ground pearls, Margarodid scales, giant scales.
Geographical distribution: World-wide. The family contains about 100 species in 10 genera.
Morphology: These are large scales whose body is segmented and usually covered by wax; the females of many species place their eggs into a white ovisac. Spiracles are located in the thoracic as well as the abdominal segments and the legs and antennae are well developed. There is no anal ring.The males are winged.
Life cycle: A life cycle may require some weeks and each female deposits several hundred eggs into the ovisac. The bodies of root-feeding species may be covered with a pearl-like waxy cover. Some may have a prolonged subterranean existence within their cysts. Both female and male development is characterised by an apodous, feeding 2nd-instar nymph, called a cyst. The cyst is primarily circular and often colourful, shiny, metallic or pearl–like, from which the common name “ground pearls” is derived. Other unique features are the strongly developed prothoracic legs for digging, the construction of a protective test from their own liquid excreta in which the cyst is enclosed and a behavioral adaptation by modification of their life-cycle to survive in adverse environmental conditions.
Economic importance: This family contains several major plant pests, such as the cottony-cushion or fluted scale, Icerya purchasi Maskell.
Management: The pest species may be controlled with white oils, although the main pest species, the cottony-cushion scale, is usually controlled by its natural enemies.
Reference
Ben-Dov, Y. 2005. A Systematic Catalogue of the Scale Insect Family Margarodidae (Hemiptera: Coccoidea) of the World. Springer, New York.
Foldi, I. 2005. Ground pearls: a generic revision of the Margarodidae sensu stricto (Hemiptera: Sternorrhyncha: Coccoidea). Annales de la Société entomologique de France (n.s.), 41: 81-125.
Hodgson, C. and Foldi, I. 2006. A review of the Margarodidae sensu Morrison (Hemiptera: Coccoidea) and some related taxa based on the morphology of adult male. Zootaxa 1263: 1-250.
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