Editing Scale insect (section)

{{short description|Superfamily of insects}}
{{good article}}
{{Automatic taxobox
| fossil_range = {{fossilrange|Kimmeridgian|0|[[Late Jurassic]] – [[Holocene|Recent]] }}
| image = Wax Scale.jpg
| image_caption = Waxy scales on [[cycad]] leaf
| taxon = Coccoidea
| authority = [[Anton Handlirsch|Handlirsch]], 1903&nbsp;<ref>{{ITIS |id=109195 |taxon=Coccoidea Handlirsch, 1903}}</ref>
| parent_authority = [[George Heslop-Harrison|Heslop-Harrison]], 1952
| display_parents = 3
| subdivision_ranks = Families
| subdivision = [[#Evolution|See text]]
}}

'''Scale insects''' are small [[insect]]s of the [[Order (biology)|order]] [[Hemiptera]], suborder [[Sternorrhyncha]]. Of dramatically variable appearance and extreme [[sexual dimorphism]], they comprise the infraorder '''Coccomorpha''' which is considered a more convenient grouping than the superfamily '''Coccoidea''' due to taxonomic uncertainties. Adult females typically have soft bodies and no limbs, and are concealed underneath domed scales, extruding quantities of wax for protection. Some species are hermaphroditic, with a combined ovotestis instead of separate ovaries and testes. Males, in the species where they occur, have legs and sometimes wings, and resemble small flies. Scale insects are [[herbivore]]s, piercing plant tissues with their mouthparts and remaining in one place, feeding on [[sap]]. The excess fluid they imbibe is secreted as [[Honeydew (secretion)|honeydew]] on which sooty mold tends to grow. The insects often have a [[Mutualism (biology)|mutualistic relationship]] with [[ant]]s, which feed on the honeydew and protect them from [[Predation|predators]]. There are about 8,000 described species.

The oldest fossils of the group date to the [[Late Jurassic]], preserved in [[amber]]. They were already substantially diversified by the [[Early Cretaceous]] suggesting an earlier origin during the [[Triassic]] or [[Jurassic]]. Their closest relatives are the [[Psylloidea|jumping plant lice]], [[Whitefly|whiteflies]], [[Phylloxeroidea|phylloxera bugs]] and [[Aphididae|aphids]]. The majority of female scale insects remain in one place as adults, with newly hatched nymphs, known as "crawlers", being the only mobile life stage, apart from the short-lived males. The reproductive strategies of many species include at least some amount of [[asexual reproduction]] by [[parthenogenesis]].

Some scale insects are serious commercial pests, notably the cottony cushion scale (''[[Icerya purchasi]]'') on ''[[Citrus]]'' fruit trees; they are difficult to control as the scale and waxy covering protect them effectively from contact insecticides. Some species are used for [[biological control]] of pest plants such as the prickly pear, ''[[Opuntia]]''. Others produce commercially valuable substances including [[carmine]] and [[kermes (dye)|kermes]] dyes, and [[shellac]] lacquer. The two red colour-names [[crimson]] and [[Scarlet (color)|scarlet]] both derive from the names of [[Kermes (insect)|''Kermes'']] products in other languages.