Editing Scale insect

{{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.

==Description==
[[File:Armored scale insects.png|thumb|Armoured scale insects:(A) ''Lepidosaphes gloverii'', adult females. (B) ''Parlatoria oleae'', adult females (circular, with dark spot) and immatures (oblong). (C) ''Diaspidiotus juglansregiae'', adult female walnut scale with waxy scale cover removed.]]

Scale insects vary dramatically in appearance, from very small organisms (1–2&nbsp;mm) that grow beneath [[wax]] covers (some shaped like oysters, others like mussel shells), to shiny pearl-like objects (about 5&nbsp;mm), to animals covered with mealy wax. Adult females are almost always immobile (apart from [[mealybug]]s) and permanently attached to the plant on which they are feeding.  They secrete a waxy coating for defence, making them resemble [[scale (zoology)|reptilian or fish scales]], and giving them their common name.<ref name=Capinera/> The key character that sets apart the Coccomorpha from all other Hemiptera is the single segmented tarsus on the legs with only one claw at the tip.<ref>{{cite journal |last1=Hodgson |first1=Chris |last2=Denno |first2=Barb |last3=Watson |first3=Gillian W. |date=2021 |title=The Infraorder Coccomorpha (Insecta: Hemiptera) |url=https://www.biotaxa.org/Zootaxa/article/view/zootaxa.4979.1.24 |journal=Zootaxa |volume=4979 |issue=1 |pages=226–227 |doi=10.11646/zootaxa.4979.1.24 |pmid=34186999 |s2cid=235685337 |doi-access=free }}</ref>

The group is extremely [[sexual dimorphism|sexually dimorphic]]; female scale insects, unusual for Hemiptera, retain the immature external morphology even when sexually mature, a condition known as [[neoteny]]. Adult females are pear-shaped, elliptical or circular, with no wings, and usually no constriction separating the head from the body. Segmentation of the body is indistinct, but may be indicated by the presence of marginal bristles. Legs are absent in the females of some families, and when present vary from single segment stubs to five-segmented limbs. Female scale insects have no compound eyes, but [[Simple eye in invertebrates#Ocelli or eye spots|ocelli]] (simple eyes) are sometimes present in [[Margarodidae]], [[Ortheziidae]] and [[Phenacoleachiidae]]. The family [[Beesoniidae]] lacks [[Antenna (biology)|antennae]], but other families possess antennae with from one to thirteen segments. The mouthparts are adapted for piercing and sucking.<ref name=Capinera/>

Adult males in contrast have the typical head, thorax and abdomen of other insect groups, and are so different from females that pairing them as a species is challenging. They are usually slender insects resembling [[aphid]]s or small [[Fly|flies]]. They have antennae with nine or ten segments, compound eyes (Margarodidae and Ortheziidae) or simple eyes (most other families), and legs with five segments.
Most species have wings, and in some, generations may alternate between being winged and wingless. Adult males do not feed, and die within two or three days of emergence.<ref name=Capinera>{{cite book |last=Capinera |first=John L. |title=Encyclopedia of Entomology |url=https://books.google.com/books?id=i9ITMiiohVQC&pg=PA3263 |year=2008 |publisher=Springer Science & Business Media |isbn=978-1-4020-6242-1 |pages=3263–3272}}</ref>

In species with winged males, generally only the forewings are fully functional. This is unusual among insects; it most closely resembles the situation in the [[fly|true flies]], the Diptera. However, the Diptera and Hemiptera are not closely related, and do not closely resemble each other in [[Morphology (biology)|morphology]]; for example, the tail filaments of the Coccomorpha do not resemble anything in the morphology of flies. The hind ([[Metathorax|metathoracic]]) wings are reduced, commonly to the point that they can easily be overlooked. In some species the hind wings have [[hamuli]], hooklets, that couple the hind wings to the main wings, as in the [[Hymenoptera]]. The [[Vestigiality|vestigial]] wings are often reduced to pseudo-[[halteres]], club-like appendages, but these are not [[Homology (biology)|homologous]] with the control organs of Diptera, and it is not clear whether they have any substantial control function.<ref>{{cite book |last=Dhooria |first=Manjit S. |title=Ane's Encyclopedic Dictionary of General & Applied Entomology |url=https://books.google.com/books?id=ybNCAAAAQBAJ&pg=PA198 |year=2009 |publisher=Springer Science & Business Media |isbn=978-1-4020-8644-1 |page=198}}</ref>

[[Hermaphrodite|Hermaphroditism]] is very rare in insects, but several species of ''[[Icerya]]'' exhibit an unusual form. The adult possesses an ovotestis, consisting of both female and male reproductive tissue, and sperm is transmitted to the young for their future use. The fact that a new population can be founded by a single individual may have contributed to the success of the [[Icerya purchasi|cottony cushion scale]] which has spread around the world.<ref>{{cite journal |last1=Gardner | first1=A. | last2=Ross | first2=L. |title=The evolution of hermaphroditism by an infectious male-derived cell lineage: an inclusive-fitness analysis |journal=The American Naturalist |volume=178 |issue=2 |pages=191–201 |year=2011 |url=https://pure.rug.nl/ws/files/67294482/660823.pdf |hdl=11370/c2d17516-c096-4e53-80a1-d79b3aab10b3 |s2cid=15361433 |hdl-access=free |doi=10.1086/660823 |pmid=21750383 }}</ref>

==Life cycle==
[[File:EB1911 Hemiptera - Fig. 13.—Apple Scale Insect (Mytilaspis pomorum).jpg|thumb|Life-cycle of the [[apple]] scale, ''Mytilaspis pomorum''. a) underside of scale showing female and eggs, x24 b)&nbsp;scale upperside, x24 c) female scales on twig d) male scale, x12 e) male scales on twig]]

Female scale insects in more advanced families develop from the egg through a first [[instar]] (crawler) stage and a second instar stage before becoming adult. In more primitive families there is an additional instar stage. Males pass through a first and second instar stage, a pre-pupal and a pupal stage before adulthood (actually a pseudopupa, as only [[Holometabolism|holometabolous]] insects have a true pupa).<ref name=Capinera/>

The first instars of most species of scale insects emerge from the egg with functional legs, and are informally called "crawlers". They immediately crawl around in search of a suitable spot to settle down and feed. In some species they delay settling down either until they are starving, or until they have been blown away by wind onto what presumably is another plant, where they may establish a new colony. There are many variations on such themes, such as scale insects that are associated with species of ants that act as herders and carry the young ones to protected sites to feed. In either case, many such species of crawlers, when they moult, lose the use of their legs if they are female, and stay put for life. Only the males retain legs, and in some species wings, and use them in seeking females. To do this they usually walk, as their ability to fly is limited, but they may get carried to new locations by the wind.<ref name=Capinera/>

[[File:EB1911 Hemiptera - Fig. 12.—Apple Scale Insect.jpg|thumb|left|Apple scale. a) male, with legs and wings b) foot of male c) larva, x20 d) antenna of larva e) immobile female (removed from scale)]]

Adult females of the families Margarodidae, Ortheziidae and Pseudococcidae are mobile and can move to other parts of the host plant or even adjoining plants, but the mobile period is limited to a short period between moults. Some of these overwinter in crevices in the bark or among plant litter, moving in spring to tender young growth. However, the majority of female scale insects are sedentary as adults. Their dispersal ability depends on how far a crawler can crawl before it needs to shed its skin and start feeding. There are various strategies for dealing with deciduous trees. On these, males often feed on the leaves, usually beside the veins, while females select the twigs. Where there are several generations in the year, there may be a general retreat onto the twigs as fall approaches. On branches, the underside is usually preferred as giving protection against predation and adverse weather. The [[Phenacoccus solenopsis|solenopsis mealybug]] feeds on the foliage of its host in summer and the roots in winter, and large numbers of scale species feed invisibly, year-round on roots.<ref name="Capinera" />

=== Reproduction and the genetics of sex determination ===

Scale insects show a very wide range of variations in the genetics of sex determination and the modes of reproduction. Besides [[sexual reproduction]], a number of different forms of reproductive systems are employed, including [[asexual reproduction]] by [[parthenogenesis]]. In some species, sexual and asexual populations are found in different locations, and in general, species with a wide geographic range and a diversity of plant hosts are more likely to be asexual. Large population size is hypothesized to protect an asexual population from becoming extinct, but nevertheless, parthenogenesis is uncommon among scale insects, with the most widespread generalist feeders reproducing sexually, the majority of these being pest species.<ref>{{cite journal |last1=Ross |first1=Laura |last2=Hardy |first2=Nate B. |last3=Okusu |first3=Akiko |last4=Normark |first4=Benjamin B. |year=2013 |title=Large population size predicts the distribution of sexuality in scale insects |journal=Evolution |volume=67 |issue=1 |pages=196–206 |doi=10.1111/j.1558-5646.2012.01784.x |pmid=23289572|doi-access=free }}</ref>

[[File:Drosicha_Lefroy.jpg|thumb|A winged male ''Drosicha'' sp.]]

Many species have the XX-XO system where the female is [[Ploidy|diploid]] and homogametic while the male is [[Heterogametic sex|heterogametic]] and missing a sex chromosome. In some [[Diaspididae]] and [[Pseudococcidae]], both sexes are produced from fertilized eggs but during development males eliminate the paternal genome and this system called paternal genome elimination (PGE) is found in nearly 14 scale insect families. This elimination is achieved with several variations. The commonest (known as the lecanoid system) involved deactivation of the paternal genome and elimination at the time of sperm production in males, this is seen in Pseudococcidae, [[Kerriidae]] and some [[Eriococcidae]]. In the other variant or ''[[Comstockiella]]'' system, the somatic cells have the paternal genome untouched. A third variant found in Diaspididae involves the paternal genome being completely removed at an early stage making males haploid both in somatic and germ cells even though they are formed from diploids, i.e., from fertilized eggs. In addition to this there is also true haplodiploidy with females born from fertilized eggs and males from unfertilized eggs. This is seen in the genus ''[[Icerya]]''. In ''[[Parthenolecanium]]'', males are born from unfertilized eggs but diploidy is briefly restored by fusion of haploid cleave nuclei and then one sex chromosome is lost through heterochromatinization. Females can reproduce parthenogenetically with six different variants based on whether males are entirely absent or not (obligate v. facultative parthenogenesis); the sex of fertilized v. unfertilized eggs; and based on how diploidy is restored in unfertilized eggs. The evolution of these systems are thought to be the result of intra-[[Intragenomic conflict|genomic conflict]] as well as possibly inter-genomic conflict with endosymbionts under varied selection pressures. The diversity of systems has made scale insects ideal models for research.<ref>{{cite journal |last1=Ross |first1=Laura |last2=Pen |first2=Ido |last3=Shuker |first3=David M. |date=2010 |title=Genomic Conflict in Scale Insects: the causes and consequences of bizarre genetic systems |journal=Biological Reviews |volume=85 |issue=4|pages=807–828 |doi=10.1111/j.1469-185X.2010.00127.x|pmid=20233171 |s2cid=13719072 }}</ref>

==Ecology==
[[File:Scale Insects (2127992762).jpg|thumb|upright|A cluster of scale insects on a stem]]

Scale insects are an ancient group, having originated in the [[Cretaceous]], the period in which [[angiosperm]]s came to dominance among plants, with only a few groups species found on [[gymnosperm]]s. They feed on a wide variety of plants but are unable to survive long away from their hosts. While some specialise on a single plant species (monophagous), and some on a single genus or plant family (oligophagous), others are less specialised and feed on several plant groups (polyphagous).<ref name=Capinera/> The parasite biologist [[Robert Poulin (zoologist)|Robert Poulin]] notes that the feeding behaviour of scale insects closely resembles that of [[ectoparasite]]s, living on the outside of their host and feeding only on them, even if they have not traditionally been so described; in his view, those species that remain immobile on a single host and feed only on it behave as obligate ectoparasites.<ref name=Rollinson>{{cite book |last=Poulin |first=Robert |author-link=Robert Poulin (zoologist) |editor1=Rollinson, D. |editor2=Hay, S. I. |title=The Many Roads to Parasitism: A Tale of Convergence |chapter=The Many Roads to Parasitism |series=Advances in Parasitology |chapter-url=https://books.google.com/books?id=9y4AlXka7t0C&pg=PA28 |year=2011 |volume=74 |publisher=Academic Press |isbn=978-0-12-385897-9 |pages=27–28 |doi=10.1016/B978-0-12-385897-9.00001-X |pmid=21295676 }}</ref> 
For example, [[Dactylopiidae|cochineal species]] are restricted to cactus hosts, and the gall-inducing ''[[Apiomorpha]]'' are restricted to ''[[Eucalyptus]]''. Some species have certain habitat requirements; some Ortheziidae occur in damp meadows, among mosses and in woodland soil, and the [[boreal ensign scale]] (''Newsteadia floccosa'') inhabits [[plant litter]].<ref name=Capinera/> A Hawaiian mealybug ''[[Clavicoccus erinaceus]]'' that fed solely on the now critically endangered ''[[Abutilon sandwicense]]'' has gone extinct as has another species ''[[Phyllococcus|Phyllococcus oahuensis]]''.<ref>{{Cite journal |last1=Moir |first1=Melinda L. |last2=Hughes |first2=Lesley|last3=Vesk |first3=Peter A. |last4=Leng |first4=Mei Chen |date=2014 |title=Which host-dependent insects are most prone to coextinction under changed climates? |journal=Ecology and Evolution |volume=4 |issue=8 |pages=1295–1312 |doi=10.1002/ece3.1021 |pmc=4020690 |pmid=24834327|bibcode=2014EcoEv...4.1295M }}</ref> Several other monophagous scale insects, especially those on islands, are threatened by [[coextinction]] due to threats faced by their host plants.<ref>{{Cite journal |last1=Thacker|first1=Jonathan I.|last2=Hopkins |first2=Graham W. |last3=Dixon |first3=Anthony F. G. |date=2006 |title=Aphids and scale insects on threatened trees: co-extinction is a minor threat|journal=Oryx |volume=40 |issue=2 |pages=233–236 |doi=10.1017/S0030605306000123 |doi-access=free}}</ref>

Most scale insects are [[herbivore]]s, feeding on [[phloem]] [[sap]] drawn directly from the plant's vascular system, but a few species feed on fungal mats and [[fungi]], such as some species in the genus ''[[Newsteadia]]'' in the family Ortheziidae. Plant sap provides a liquid diet which is rich in sugar and non-essential amino acids. In order to make up for the shortage of essential amino acids, they depend on endosymbiotic proteobacteria.<ref>{{Cite journal |last=Moran |first=Nancy A. |date=2001 |title=The coevolution of bacterial endosymbionts and phloem-feeding insects |journal=Annals of the Missouri Botanical Garden |volume=88 |issue=1 |pages=35–44 |doi=10.2307/2666130 |jstor=2666130 |url=https://www.biodiversitylibrary.org/part/38840 }}</ref>  Scale insects secrete a large quantity of sticky viscid fluid known as "[[Honeydew (secretion)|honeydew]]". This includes sugars, amino acids and minerals, and is attractive to ants as well as acting as a [[Substrate (biology)|substrate]] on which [[sooty mould]] can grow. The mould can reduce [[photosynthesis]] by the leaves and detracts from the appearance of ornamental plants. The scale's activities can result in stress for the plant, causing reduced growth and giving it a greater susceptibility to plant diseases.<ref>{{cite book |last1=Stauffer |first1=S. |last2=Rose |first2=M. |title=Soft Scale Insects |url=https://books.google.com/books?id=QjMzWX2hB1EC&pg=PA186 |year=1997 |publisher=Elsevier |isbn=978-0-08-054135-8 |pages=186–187}}</ref>

[[File:Formica fusca and mealy bugs.jpg|thumb|upright|left|[[Mutualism (biology)|Mutualistic]] ''[[Formica fusca]]'' ants tending a herd of [[mealybugs]]]]

Scale insects in the genus ''[[Cryptostigma]]'' live inside the nests of neotropical ant species.<ref>{{cite journal|doi=10.1590/S1519-566X2004000600009 |title=A new species of ant-tended soft scale of the genus ''Cryptostigma'' Ferris (Hemiptera: Coccidae) associated with bamboo in Peru |year=2004 |last1=Kondo |first1=Takumasa |last2=Gullan |first2=Penny J. |journal=Neotropical Entomology |volume=33 |issue=6 |pages=717–723 |doi-access=free }}</ref> Many tropical plants need ants to survive which in turn cultivate scale insects thus forming a [[tripartite symbiosis]].<ref>{{cite journal |doi=10.1098/rspb.2008.0573 |jstor=25249807 |title=An ancient tripartite symbiosis of plants, ants and scale insects |year=2008 |last1=Itino |first1=Takao |last2=Murase |first2=Kaori |last3=Sato |first3=Yumiko |last4=Inamori |first4=Keita |last5=Itioka |first5=Takao |last6=Quek |first6=Swee-Peck |last7=Ueda |first7=Shouhei |journal=Proceedings of the Royal Society B: Biological Sciences |volume=275 |issue=1649 |pmid=18611850 |pages=2319–26 |pmc=2603224}}</ref> Some ants and scale insects have a [[Mutualism (biology)|mutualistic]] relationship; the ants feed on the honeydew and in return protect the scales. On a [[tulip tree]], ants have been observed building a papery tent over the scales. In other instances, scale insects are carried inside the ant's nest; the ant ''[[Acropyga exsanguis]]'' takes this to an extreme by transporting a fertilised female mealybug with it on its nuptial flight, so that the nest it founds can be provisioned.<ref name=Capinera/> This provides a means for the mealybug to be dispersed widely. Species of ''[[Hippeococcus]]'' have long clinging legs with claws to grip the ''[[Dolichoderus]]'' ants which tend them; they allow themselves to be carried into the ant colony. Here the mealybugs are safe from predation and environmental hazards, while the ants have a source of nourishment.<ref name=Capinera/> Another species of ant maintains a herd of scale insects inside the hollow stems of a ''[[Barteria]]'' tree; the scale insects feed on the sap and the ants, while benefiting from the honeydew, drive away other herbivorous insects from the tree as well as preventing vines from smothering it.<ref>{{cite book |last1=Hölldobler |first1=Bert |last2=Wilson |first2=Edward O. |author2-link=E. O. Wilson |title=The Ants |url=https://archive.org/details/ants0000hlld |url-access=registration |year=1990 |publisher=Harvard University Press |isbn=978-0-674-04075-5 |page=[https://archive.org/details/ants0000hlld/page/553 553]}}</ref>

[[File:Ladybug(india).jpg|thumb|''[[Cheilomenes sexmaculata]]'' [[Predation|preying]] on mealybugs]]

Scale insects have various natural enemies, and research in this field is largely directed at the species that are crop pests. [[Entomopathogenic fungus|Entomopathogenic fungi]] can attack suitable scales and completely overgrow them. The identity of the host is not always apparent as many fungi are host-specific, and may destroy all the scales of one species present on a leaf while not affecting another species.<ref>{{cite book |last1=Evans |first1=Harry C. |last2=Hywel-Jones |first2=Nigel L. |title=Soft Scale Insects |url=https://books.google.com/books?id=QjMzWX2hB1EC&pg=PA3 |year=1997 |publisher=Elsevier |isbn=978-0-08-054135-8 |pages=3–4}}</ref> Fungi in the genus ''[[Septobasidium]]'' have a more complex, mutualistic relationship with scale insects. The fungus lives on trees where it forms a mat which overgrows the scales, reducing the growth of the individual parasitised scales and sometimes rendering them infertile, but protecting the scale colony from environmental conditions and predators. The fungus benefits by metabolising the sap extracted from the tree by the insects.<ref>{{cite web |title=The genus ''Septobasidium'' |work=The genome portal of the Department of Energy Joint Genome Institute |url=https://genome.jgi.doe.gov/Sepsp1/Sepsp1.home.html |publisher=Fungal Genomics Resource |access-date=18 January 2020}}</ref>

Natural enemies include [[parasitoid wasp]]s, mostly in the families [[Encyrtidae]] and [[Eulophidae]], and [[Predation|predatory]] beetles such as [[Anthribidae|fungus weevils]], [[Coccinellidae|ladybirds]] and [[sap beetle]]s.<ref name=Capinera/> Ladybirds feed on aphids and scale insects, laying their eggs near their prey to ensure their larvae have immediate access to food. The ladybird ''[[Cryptolaemus montrouzieri]]'' is known as the "mealybug destroyer" because both adults and larvae feed on mealybugs and some soft scales.<ref>{{Cite web|url=http://www.entomology.wisc.edu/mbcn/kyf205.html|title=Know Your Friends - Mealybug Destroyer|date=14 February 2009|publisher=www.entomology.wisc.edu [[University of Wisconsin]]|access-date=16 January 2020|archive-url=https://web.archive.org/web/20120216004540/http://www.entomology.wisc.edu/mbcn/kyf205.html|archive-date=16 February 2012|url-status=dead}}</ref> Ants looking after their providers of honeydew tend to drive off predators, but the mealybug destroyer has outwitted the ants by developing cryptic camouflage, with their larvae mimicking scale larvae.<ref name=Capinera/>

==Significance==

===As pests===

Many scale species are serious crop [[pest (animal)|pest]]s and are particularly problematic for their ability to evade [[Pest quarantine|quarantine]] measures.<ref>{{Cite journal |last1=Sethusa |first1=M.T. |last2=Millar |first2=I.M. |last3=Yessoufou |first3=K. |last4=Jacobs |first4=A. |last5=Bank |first5=M. van der |last6=Bank |first6=H. van der |date=2014 |title=DNA Barcode Efficacy for the Identification of Economically Important Scale Insects (Hemiptera: Coccoidea) in South Africa |url=http://www.bioone.org/doi/abs/10.4001/003.022.0218 |journal=African Entomology |language=en |volume=22 |issue=2 |pages=257–266 |doi=10.4001/003.022.0218 |s2cid=84171305 |issn=1021-3589|url-access=subscription }}</ref><ref name="ISU">{{cite web |title=Scale Insects |url=https://hortnews.extension.iastate.edu/scale-insects |publisher=Iowa State University |access-date=14 January 2020}}</ref> In 1990, they caused around $5&nbsp;billion of damage to crops in the United States.<ref name="Piper2011">{{cite book |last=Piper |first=Ross |title=Pests: A Guide to the World's Most Maligned, Yet Misunderstood Creatures |url=https://books.google.com/books?id=wRDIOhoQR68C&pg=PA149 |year=2011 |publisher=ABC-CLIO |isbn=978-0-313-38426-4 |page=149}}</ref>
The waxy covering of many species of scale protects their adults effectively from contact [[insecticide]]s, which are only effective against the first-instar [[Nymph (biology)|nymph]] stage known as the ''crawler''. However, scales can often be controlled using [[horticultural oil]]s that [[suffocation|suffocate]] them, systemic pesticides that poison the sap of the host plants, or by [[biological control]] agents such as tiny [[parasitoid]] wasps and ladybirds. [[Insecticidal soap]] may also be used against scales.<ref>{{cite web |title=Scale insects |url=https://www.gardenersworld.com/how-to/solve-problems/scale-insects/ |website=[[Gardeners' World]] |access-date=16 January 2020}}</ref>

One species, the cottony cushion scale, is a serious commercial pest on 65 families of woody plants, including ''[[Citrus]]'' fruits. It has spread worldwide from Australia.<ref>[http://scalenet.info/catalogue/Icerya%20purchasi/ ScaleNet]</ref><ref>{{cite book |last=Nair |first=K. S. S. |date=2007 |title=Tropical Forest Insect Pests: Ecology, Impact, and Management |url=https://books.google.com/books?id=QvOPufXCJq0C&pg=PA221 |publisher=Cambridge University Press |isbn=9781139464857 |page=221}}</ref>

<gallery class="center" mode="nolines" widths="200px" heights="200px">
File:Icerya purchasi feeding on Citrus.jpg|Adult female [[cottony cushion scale]] (''Icerya purchasi'') with young crawlers. The species is a major commercial pest of crops such as ''Citrus'' fruits.
File:Anagyrus lopezi.jpg|The tiny [[parasitic wasp]] ''[[Anagyrus|Anagyrus lopezi]]'', a highly effective biological control of the [[cassava]] mealybug
</gallery>

===As biological controls===

At the same time, some kinds of scale insects are themselves useful as biological control agents for pest plants, such as various species of [[Dactylopius|cochineal insects]] that attack [[invasive species]] of [[Opuntia|prickly pear]], which spread widely especially in [[Prickly pears in Australia|Australia]] and Africa.<ref name=Ramirez>{{cite journal|last=Ramírez-Puebla |first=S. T. |year=2010 |url=http://www.bashanfoundation.org/martinez/martinezdactylopius.pdf |title=Molecular phylogeny of the genus ''Dactylopius'' (Hemiptera: Dactylopiidae) and identification of the symbiotic bacteria |archive-url=https://web.archive.org/web/20150923182527/http://www.bashanfoundation.org/martinez/martinezdactylopius.pdf |archive-date=2015-09-23 |journal=Environmental Entomology |volume=39 |issue=4 |pages=1178–83 |doi=10.1603/EN10037 |pmid=22127169 |s2cid=5816903 |doi-access=free }}</ref><ref name="cabi">{{cite web |title=''Opuntia ficus-indica'' (prickly pear) |url=https://www.cabi.org/isc/datasheet/37714 |publisher=CABI |date=3 January 2018}}</ref>

===Products===

Some types of scale insect are economically valuable for the substances they can yield under proper husbandry. Some, such as the [[cochineal]], [[Kermes (insect)|kermes]], [[lac scale|lac]], [[Armenian cochineal]], and [[Polish cochineal]], have been used to produce red dyes for coloring foods and dyeing fabrics.<ref>{{cite web |url=http://www.fao.org/docrep/v8879e/v8879e09.htm |title=Cochineal and Carmine |work=Major colourants and dyestuffs, mainly produced in horticultural systems |publisher=FAO |access-date=June 16, 2015}}</ref><ref>{{cite web |url=https://www.fda.gov/ForIndustry/ColorAdditives/GuidanceComplianceRegulatoryInformation/ucm153038.htm |archive-url=https://web.archive.org/web/20090606162207/http://www.fda.gov/ForIndustry/ColorAdditives/GuidanceComplianceRegulatoryInformation/ucm153038.htm |url-status=dead |archive-date=June 6, 2009 |title=Guidance for Industry: Cochineal Extract and Carmine |publisher=FDA |access-date=6 July 2016}}</ref><ref name="Munro214">{{cite book |last=Munro |first=John H. |chapter=4: Medieval Woollens: Textiles, Technology, and Organisation c. 800–1500|editor=Jenkins, David |year=2003 |title=The Cambridge History of Western Textiles |volume=I |publisher=Cambridge University Press |isbn=0-521-34107-8 |oclc=48475172 |pages=214–215 |chapter-url=https://archive.org/details/cambridgehistory0000unse_l9b6/page/214/mode/1up?view=theater&q=%22Kermes+%28Kermococcus%29+vermilio%22 }}</ref> Both the colour name "[[crimson]]" and the generic name ''Kermes'' are from Italian ''carmesi'' or ''cremesi'' for the dye used for Italian silk textiles, in turn from the Persian<ref>{{cite web |last1=ویکی |first1=پارسی |title=معنی قرمز {{!}} لغت نامه دهخدا |url=https://www.parsi.wiki/fa/wiki/345624/%D9%82%D8%B1%D9%85%D8%B2 |website=پارسی ویکی |access-date=3 April 2021 |language=fa}}</ref> ''qirmizī'' (قرمز), meaning both the colour and the insect.<ref>{{cite web |title=Crimson (n.) |url=https://www.etymonline.com/word/crimson |publisher=Etymology Online |access-date=17 January 2020}}</ref> The colour name "[[Scarlet (color)|scarlet]]" is similarly derived from Arabic ''siklāt'', denoting extremely expensive luxury silks dyed red using kermes.<ref>{{Cite encyclopedia |last=Munro |first=John |year=2012 | chapter=Scarlet |editor=Gale Owen-Crocker |editor2=Elizabeth Coatsworth |editor3=Maria Hayward |title=Encyclopedia of Medieval Dress and Textiles |publisher=Brill | doi=10.1163/2213-2139_emdt_COM_550 |isbn=978-9004124356 }}</ref>

Some waxy scale species in the genera ''[[Ceroplastes]]'' and ''[[Ericerus]]'' produce materials such as [[Chinese wax]],<ref>{{cite book|author=Zhang, Xiaoming |title=Chinese Furniture|url=https://books.google.com/books?id=uT-2qaTOYEsC&pg=PA58 |year=2011|publisher=Cambridge University Press|isbn=978-0-521-18646-9 |page=58}}</ref> and several genera of [[lac scale]]s produce [[shellac]].<ref>{{cite news |title=How Shellac Is Manufactured |url=http://nla.gov.au/nla.news-article55073762 |publisher=The Mail (Adelaide, SA : 1912 – 1954) |date=18 Dec 1937}}</ref>

<gallery class="center" mode="nolines" widths="200px" heights="200px">
File:Indian collecting cochineal.jpg|Collecting scale insects from a prickly pear for a [[dyestuff]], cochineal, 1777
File:Weltliche Schatzkammer Wienc.jpg|Coronation cloak of King [[Roger II of Sicily]], 1133. Silk [[Scarlet (cloth)|scarlet cloth]] dyed with [[Kermes (dye)|kermes]], made from female ''Kermes'' scales
File:Shellac varities.png|Some varieties of shellac
File:02-Indian-Insect-Life - Harold Maxwell-Lefroy - Kerria-Lacca.jpg|''[[Kerria lacca]]'' and its shellac tubes
</gallery>

==Evolution==

The containing group of the scale insects was formerly treated as the superfamily Coccoidea but taxonomic uncertainties have led workers to prefer the use of the infraorder Coccomorpha as the preferred name for the group.<ref>{{cite journal |last1=Williams |first1=Douglas J. |last2=Hodgson |first2=Chris J. |date=2014 |title=The case for using the infraorder Coccomorpha above the superfamily Coccoidea for the scale insects (Hemiptera: Sternorrhyncha) |url=http://biotaxa.org/Zootaxa/article/view/zootaxa.3869.3.9 |journal=Zootaxa |volume=3869 |issue=3 |pages=348–350 |doi=10.11646/zootaxa.3869.3.9 |pmid=25283922 |doi-access=free }}</ref> Scale insects are members of the [[Sternorrhyncha]]. The [[phylogeny]] of the extant groups, inferred from analysis of small subunit (18S) [[ribosomal RNA]], is shown in the first [[cladogram]].{{Cn|date=May 2023}}

{{clade
|label1=[[Sternorrhyncha]]
|1={{clade
   |1=[[Psylloidea]] (jumping plant lice, etc) [[File:Psyllia_pyricola.png|125px]]
   |2={{clade
      |1=[[Aleyrodoidea]] (whiteflies) [[File:Neomaskellia bergii from CSIRO.jpg|90px]]
      |2={{clade
         |1='''Coccomorpha''' (scale insects) [[File:Ceroplastes_ceriferus_from_CSIRO.jpg|90px]]
         |label2=[[Aphidomorpha]]
         |2={{clade
            |1=[[Phylloxeroidea]] (phylloxera bugs) [[File:Daktulosphaira vitifoliae from CSIRO.jpg|60px]]
            |2=[[Aphididae]] (aphids) [[File:Aphid_winged.jpg|90px]]
            }}
         }}
      }}
   }}
}}

[[File:Acropyga glaesaria SMFBE457B2 01.jpg|thumb|Fossil of the [[Pseudococcidae|pseudococcid]] mealybug ''[[Electromyrmococcus]]'' (in the jaws of an ant) in [[Miocene]] [[Dominican amber]]<ref name="Poinar2011">{{cite journal |last1=Poinar |first1=G. |last2=Heiss |first2=E. |year=2011 |title=New Termitaphididae and Aradidae (Hemiptera) in Mexican and Dominican amber |journal=Palaeodiversity |volume=4 |pages=51–62 |url=http://www.palaeodiversity.org/pdf/04/Palaeodiversity_4_PoinarHeiss.pdf}}</ref>]]

The timing of phylogenetic diversification within the Coccomorpha was estimated in a 2016 study based on [[molecular clock]] divergence time estimates, along with fossils being used for calibration. They suggested that the main scale insect lineages diverged before their angiosperm hosts, and suggested that the insects switched from feeding on gymnosperms once the angiosperms became common and widespread in the Cretaceous. They estimated that the Coccomorpha appeared at the start of the [[Triassic]] period, around 245 million years ago, and that the neococcoids appeared during the Early Jurassic, some 185 million years ago.<ref name="VeaGrimaldi2016" /> Scale insects are very well represented in the fossil record, with the oldest known member of the group reported from the [[Late Jurassic]] [[amber]] from Lebanon.<ref name=Jankotejacoccidae>{{Cite journal|last1=Vršanský |first1=P. |last2=Sendi |first2=H. |last3=Kotulová |first3=J. |last4=Szwedo |first4=J. |last5=Havelcová |first5=M. |last6=Palková |first6=H. |last7=Vršanská |first7=L. |last8=Sakala |first8=J. |last9=Puškelová |first9=L. |last10=Golej |first10=M. |last11=Biroň |first11=A. |last12=Peyrot |first12=D. |last13=Quicke |first13=D. |last14=Néraudeau |first14=D. |last15=Uher |first15=P. |last16=Maksoud |first16=S. |last17=Azar |first17=D. |title=Jurassic Park approached: a coccid from Kimmeridgian cheirolepidiacean Aintourine Lebanese amber |year=2024 |journal=National Science Review |at=nwae200 |doi=10.1093/nsr/nwae200 |doi-access=free |pmc=11895504 }}</ref> They are abundantly preserved in amber from the Early Cretaceous, 130 mya, onwards; they were already highly diversified by Cretaceous times. All the families were monophyletic except for the [[Eriococcidae]]. The Coccomorpha are division into two clades the "Archaeococcoids" and "Neococcoids". The archaeococcoid  families have adult males with either compound eyes or a row of unicorneal eyes and have abdominal spiracles in the females. In neoccoids, the females have no abdominal spiracles.<ref>{{cite journal |last1=Williams |first1=D. J. |last2=Gullan |first2=P. J. |last3=Miller |first3=D. R. |last4=Matile-Ferrero |first4=D. |last5=Han |first5=Sarah I. |date=2011 |title=A study of the scale insect genera Puto Signoret (Hemiptera: Sternorrhyncha: Coccoidea: Putoidae) and Ceroputo Šulc (Pseudococcidae) with a comparison to Phenacoccus Cockerell (Pseudococcidae) |url=https://biotaxa.org/Zootaxa/article/view/zootaxa.2802.1.1 |journal=Zootaxa |volume=2802 |issue=1 |pages=1 |doi=10.11646/zootaxa.2802.1.1 |hdl=1885/63136 |hdl-access=free }}</ref> In the cladogram below the genus ''Pityococcus'' is moved to the "Neococcoids". A cladogram showing the major families using this methodology is shown below.<ref name="VeaGrimaldi2016">{{cite journal |last1=Vea |first1=Isabelle M. |last2=Grimaldi |first2=David A. |title=Putting scales into evolutionary time: the divergence of major scale insect lineages (Hemiptera) predates the radiation of modern angiosperm hosts |journal=Scientific Reports |volume=6 |issue=1 |pages=23487 |year=2016 |issn=2045-2322 |doi=10.1038/srep23487|pmid=27000526 |pmc=4802209 |bibcode=2016NatSR...623487V }}</ref>

{{clade
|label1='''Coccomorpha'''
|1={{clade
|label1="Archaeococcoids"
|sublabel1=- ''Pityococcus''
|1={{clade
   |1={{clade
      |1=†[[Burmacoccidae]]
      |2=†[[Kozariidae]]
      }}
   |2={{clade
      |1={{clade
         |1=[[Matsucoccidae]] (pine bast scales)
         |2=[[Ortheziidae]] (ensign scales)
         }}
      |2={{clade
         |1=[[Margarodidae]] (ground pearls)
         |2={{clade
            |1=[[Kuwaniidae]]
            |2={{clade
               |1=[[Xylococcidae]]
               |2={{clade
                  |1=[[Coelostomidiidae]]
                  |2=[[Monophlebidae]] (cottony cushion scales)
                  }}
               }}
            }}
         }}
      }}
   }}
|label2="Neococcoids" 
|sublabel2=+ ''Pityococcus''
|2={{clade
   |1=[[Pityococcidae]]
   |2={{clade
      |1=[[Steingeliidae]]
      |2={{clade
         |1={{clade
            |1=[[Phenacoleachiidae]]
            |2=[[Putoidae]] (giant mealybugs)
            }}
         |2={{clade
            |1=[[Pseudococcidae]] (mealybugs)
            |2={{clade
               |1={{clade
                  |1=[[Coccidae]] (soft scales)
                  |2={{clade
                     |1=[[Kermesidae]] (kermes dye scales)
                     |2={{clade
                        |1=[[Asterolecaniidae]] (pit scales)
                        |2=[[Kerriidae]] (lac scales)
                        }}
                     }}
                  }}
               |2={{clade
                  |1={{clade
                     |1=[[Dactylopiidae]] (cochineal insects)
                     |2=''[[Palaearctic]]'' "[[Eriococcidae]]" (felted scales)
                     }}
                  |2={{clade
                     |1=[[Beesoniidae]], [[Stictococcidae]], part of "[[Eriococcidae]]"
                     |2={{clade
                        |1=[[Phoenicococcidae]] (palm scales)
                        |2=[[Diaspididae]] (armoured scales)
                        }}
                     }}
                  }}
               }}
            }}
         }}
      }}
   }}
}}
}}

Recognition of scale insect families has fluctuated over time, and the validity of many remains in flux,<ref>{{Cite journal |last1=Gullan |first1=P. J. |last2=Cook |first2=L. G. |year=2007 |title=Phylogeny and higher classification of the scale insects (Hemiptera: Sternorrhyncha: Coccoidea) |journal=Zootaxa |volume=1668 |pages=413–425 |url=http://www.mapress.com/zootaxa/list/2007/Linnaeus.html |doi=10.11646/zootaxa.1668.1.22 |url-access=subscription }}</ref><ref name="Hodgson-2013">{{cite journal |last1=Hodgson |first1=Chris J. |last2=Hardy |first2=Nate B. |year=2013 |title=The phylogeny of the superfamily Coccoidea (Hemiptera: Sternorrhyncha) based on the morphology of extant and extinct macropterous males |journal=Systematic Entomology |volume=38 |issue=4 |pages=794–804 |doi=10.1111/syen.12030 |doi-access=free |bibcode=2013SysEn..38..794H }}</ref> with several recognized families not included in the phylogeny presented above including extinct groups are listed below:<ref>{{cite journal |last=Szwedo |first=J. |year=2018 |title=The unity, diversity and conformity of bugs (Hemiptera) through time |journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh |volume=107 |issue=2–3 |pages=109–128 |doi=10.1017/s175569101700038x |s2cid=134243346 }}</ref><ref>{{cite web |last1=Ben-Dov |first1=Y. |last2=Miller |first2=D. R. |last3=Gibson |first3=G.A.P. |work=ScaleNet |url=http://www.sel.barc.usda.gov/scalenet/scalenet.htm |title=Home |access-date=2013-04-04 |url-status=dead |archive-url=https://web.archive.org/web/20130404165159/http://www.sel.barc.usda.gov/scalenet/scalenet.htm |archive-date=2013-04-04}}</ref><ref name="johnsonetal1995">{{cite journal |year=2001 |issue=335 |pages=1–18 |title=''Acropyga'' and ''Azteca'' ants (Hymenoptera: Formicidae) with scale insects (Sternorrhyncha: Coccoidea): 20 million years of intimate symbiosis |last1=Johnson |first1=Christine |last2=Agosti |first2=Donat |last3=Delabie |first3=Jacques H. |last4=Dumpert |first4=Klaus |last5=Williams |first5=D. J. |last6=von Tschirnhaus |first6=Michael |last7=Maschwitz |first7=Ulrich |display-authors=3 |journal=American Museum Novitates |doi=10.1206/0003-0082(2001)335<0001:AAAAHF>2.0.CO;2 |s2cid=55067700 |url=https://zenodo.org/record/5370690 }}</ref>

* Archecoccoidea {{small|Borchsenius, 1958}}
** {{extinct}}[[Apticoccidae]] {{small|Vea & Grimaldi, 2015}}
** {{extinct}}[[Arnoldidae]] {{small|Koteja, 2008}}
** {{extinct}}[[Burmacoccidae]] {{small|Koteja, 2004}}
** [[Callipappidae]] {{small|MacGillivray, 1921}}
** [[Coelostomidiidae]] {{small|Morrison, 1927}}
** {{extinct}}[[Electrococcidae]] {{small|Koteja, 2000}}
** {{extinct}}[[Grimaldiellidae]] {{small|Koteja, 2000}}
** {{extinct}}[[Grohnidae]] {{small|Koteja, 2008}}
** {{extinct}}[[Hammanococcidae]] {{small|Koteja & Azar, 2008}}
** {{extinct}}[[Jankotejacoccidae]] {{small|Szwedo, Azar & Sendi, 2024}}<ref name=Jankotejacoccidae />
** {{extinct}}[[Jersicoccidae]] {{small|Koteja, 2000}}
** {{extinct}}[[Kozariidae]] {{small|Vea & Grimaldi, 2015}}
** {{extinct}}[[Kukaspididae]] {{small|Koteja & Poinar, 2001}}
** [[Kuwaniidae]] {{small|MacGillivray, 1921}}
** {{extinct}}[[Labiococcidae]] {{small|Koteja, 2000b}}
** {{extinct}}[[Lebanococcidae]] {{small|Koteja & Azar, 2008}}
** [[Lithuanicoccidae]] {{small|Koteja, 2008}}
** [[Macrodrilidae]] {{small|Poinar, 2020}}<ref name="Macrodrilus2020">{{cite journal |last1=Poinar |first1=G. O. Jr |year=2020 |title=Macrodrilidae fam. nov. (Hemiptera: Sternorrhyncha: Coccoidea), a new family of scale insects in mid-Cretaceous Burmese amber |journal=Historical Biology: An International Journal of Paleobiology |volume=33 |issue=9 |pages= 1726–1730|doi=10.1080/08912963.2020.1733549 |s2cid=216480240 }}</ref>
** [[Marchalinidae]] {{small|Morrison, 1927}}
** [[Margarodidae]] {{small|Cockerell, 1899}}
** [[Matsucoccidae]] {{small|Morrison, 1927}}
** [[Monophlebidae]] {{small|Morrison, 1927}}
** [[Ortheziidae]] {{small|Amyot & Audinet-Serville, 1843}}
** {{extinct}}[[Pennygullaniidae]] {{small|Koteja & Azar, 2008}}
** [[Phenacoleachiidae]] {{small|Cockerell, 1902}}
** [[Pityococcidae]] {{small|McKenzie, 1942}}
** [[Putoidae]] {{small|Tang, 1992}}
** {{extinct}}[[Serafinidae]] {{small|Koteja, 2008}}
** [[Steingeliidae]] {{small|Morrison, 1927}}
** [[Stigmacoccidae]] {{small|Morrison, 1927}}
** [[Termitococcidae]] {{small|Jakubski, 1965}}
** {{extinct}}[[Weitschatidae]] {{small|Koteja, 2008}}
** [[Xylococcidae]] {{small|Pergande in Hubbard & Pergande, 1898}}
* Neococcoidea {{small|Borchsenius, 1950}}
** [[Aclerdidae]] {{small|Cockerell, 1905}}
** {{extinct}}[[Albicoccidae]] {{small|Koteja, 2004}}
** [[Asterolecaniidae]] {{small|Cockerell, 1896}}
** [[Beesoniidae]] {{small|Ferris, 1950}}
** [[Calycicoccidae]] {{small|Brain, 1918}}
** [[Carayonemidae]] {{small|Richard, 1986}}
** [[Cerococcidae]] {{small|Balachowsky, 1942}}
** [[Cissococcidae]] {{small|Brain, 1918}}
** [[Coccidae]] {{small|Fallen, 1814}}
** [[Conchaspididae]] {{small|Green, 1896}}
** [[Cryptococcidae]] {{small|Kosztarab, 1968}}
** [[Dactylopiidae]] {{small|Signoret, 1875}}
** [[Diaspididae]] {{small|Targioni-Tozzetti, 1868}}
** [[Eriococcoidae]] {{small|Cockerell, 1899}}
** [[Halimococcidae]] {{small|Brown & McKenzie, 1962}}
** {{extinct}}[[Hodgsonicoccidae]] {{small|Vea & Grimaldi, 2015}}
** {{extinct}}[[Inkaidae]] {{small|Koteja, 1989}}
** [[Kermesidae]] {{small|Signoret, 1875}}
** [[Kerriidae]] {{small|Lindinger, 1937}}
** [[Lecanodiaspididae]] {{small|Targioni-Tozzetti, 1869}}
** [[Micrococcidae]] {{small|Silvestri, 1939}}
** [[Phoenicococcidae]] {{small|Stickney, 1934}}
** [[Porphyrophoridae]] {{small|Signoret, 1875}}
** [[Pseudococcidae]] {{small|Cockerell, 1905}}
** [[Rhizoecidae]] {{small|Williams, 1969}}
** [[Stictococcidae]] {{small|Lindinger, 1913}}
** [[Tachardiidae]] {{small|Green, 1896}}

==See also==
*''[[Conchaspis capensis]]''
*''[[Lepidosaphes beckii]]''

==References==
{{reflist|30em}}

== External links ==
{{Wikispecies|Coccoidea}}
{{Commons category|Coccoidea}}

* [https://web.archive.org/web/20130404165159/http://www.sel.barc.usda.gov/scalenet/scalenet.htm ScaleNet homepage]
* [http://gardenbees.com/biological%20control/revolution.htm Cottony cushion scale: the pest that launched a pest control revolution]
* [http://nlbif.eti.uva.nl/bis/diaspididae.php Diaspididae of the World]
* [http://www.agri.gov.il/en/pages/10.aspx Scale Insect Forum] {{Webarchive|url=https://web.archive.org/web/20200930163921/http://www.agri.gov.il/en/pages/10.aspx |date=2020-09-30 }}
* [https://web.archive.org/web/20090226170947/http://entomology.ifas.ufl.edu/fasulo/woodypest/scales.htm Scales of southeastern U.S. woody ornamentals]

On the [[University of Florida]] / [[Institute of Food and Agricultural Sciences]] ''Featured Creatures'' website:
* [https://web.archive.org/web/20090830115316/http://entomology.ifas.ufl.edu/creatures/orn/scales/red_wax_scale.htm ''Ceroplastes rubens'', red wax scale ]
* [http://entomology.ifas.ufl.edu/creatures/orn/scales/fig_wax_scale.htm ''Ceroplastes rusci'', fig wax scale]
* [http://entomology.ifas.ufl.edu/creatures/orn/scales/green_scale.htm ''Coccus viridia'', green scale]
* [http://entomology.ifas.ufl.edu/creatures/orn/scales/tessellated_scale.htm  ''Eucalymnatus tessellatus'', tessellated scale]
* [http://entomology.ifas.ufl.edu/creatures/orn/palms/red_date_scale.htm ''Phoenicoccus marlatti'', red date scale]

{{Hemiptera|2}}
{{Taxonbar|from=Q209602|from2=Q55389125}}
{{Authority control}}

{{DEFAULTSORT:Scale Insect}}
[[Category:Scale insects| ]]
[[Category:Sternorrhyncha]]
[[Category:Agricultural pest insects]]
[[Category:Insect pests of ornamental plants]]
[[Category:Insect pests of tropical forests]]
[[Category:Extant Triassic first appearances]]