Scale insects are small

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...

s of the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...

, 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 herbivores, piercing plant tissues with their mouthparts and remaining in one place, feeding on sap. The excess fluid they imbibe is secreted as honeydew on which sooty mold tends to grow. The insects often have a mutualistic relationship with ants, which feed on the honeydew and protect them from predators. There are about 8,000 described species. The oldest fossils of the group date to the Early Cretaceous, preserved in

amber Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In M ...

. They were already substantially diversified by this time suggesting an earlier origin during the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

. Their closest relatives are the jumping plant lice, whiteflies , phylloxera bugs and 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 Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the ...

parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...

. Some scale insects are serious commercial pests, notably the cottony cushion scale ('' Icerya purchasi'') on ''

Citrus ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is native to ...

'' 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 Carmine ()also called cochineal (when it is extracted from the cochineal insect), cochineal extract, crimson lake, or carmine lake is a pigment of a bright-red color obtained from the aluminium complex derived from carminic acid. Specific code ...

and kermes dyes, and shellac lacquer. The two red colour-names

crimson Crimson is a rich, deep red color, inclining to purple. It originally meant the color of the kermes dye produced from a scale insect, '' Kermes vermilio'', but the name is now sometimes also used as a generic term for slightly bluish-red co ...

and scarlet both derive from the names of ''Kermes'' products in other languages.

Description

Scale insects vary dramatically in appearance, from very small organisms (1–2 mm) that grow beneath wax covers (some shaped like oysters, others like mussel shells), to shiny pearl-like objects (about 5 mm), to animals covered with mealy wax. Adult females are almost always immobile (apart from mealybugs) and permanently attached to the plant on which they are feeding. They secrete a waxy coating for defence, making them resemble reptilian or fish scales, and giving them their common name. 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. The group is extremely sexually dimorphic; female scale insects, unusually for Hemiptera, retain the immature external morphology even when sexually mature, a condition known as

neoteny Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compare ...

. 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 ocelli (simple eyes) are sometimes present in

Margarodidae The Margarodidae (illegitimately as Margodidae) or ground pearls are a family of scale insects within the superfamily Coccoidea. Members of the family include the Polish cochineal and Armenian cochineal (genus ''Porphyrophora'') and the original ...

Ortheziidae Ortheziidae is a family of scale insects commonly known as the ensign scales or ortheziids. They occur in most parts of the world but the majority of the species are found in the Neotropical and Nearctic regions while there are not many species i ...

and Phenacoleachiidae. The family

Beesoniidae Beesoniidae is a family of scale insects commonly known as beesoniids. They typically cause galls on their plant hosts. Members of this family mostly come from southern Asia.antennae, but other families possess antennae with from one to thirteen segments. The mouthparts are adapted for piercing and sucking. 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 aphids or small 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. 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

true flies Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...

, the Diptera. However, the Diptera and Hemiptera are not closely related, and do not closely resemble each other in morphology; for example, the tail filaments of the Coccomorpha do not resemble anything in the morphology of flies. The hind ( metathoracic) wings are reduced, commonly to the point that they can easily be overlooked. In some species the hind wings have

hamuli A hamus or hamulus is a structure functioning as, or in the form of, hooks or hooklets. Etymology The terms are directly from Latin, in which ''hamus'' means " hook". The plural is ''hami''. ''Hamulus'' is the diminutive – hooklet or little ...

, hooklets, that couple the hind wings to the main wings, as in the Hymenoptera. The vestigial wings are often reduced to pseudo- halteres, club-like appendages, but these are not homologous with the control organs of Diptera, and it is not clear whether they have any substantial control function. Hermaphroditism is very rare in insects, but several species of ''

Icerya ''Icerya'' is a genus of scale insects in the family Monophlebidae. It is named after physician-naturalist Dr. Edmond Icery of British Mauritius. Hermaphroditism Hermaphroditism is extremely rare in the insect world despite the comparatively com ...

'' 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

cottony cushion scale ''Icerya purchasi'' (common name: cottony cushion scale) is a scale insect that feeds on more than 80 families of woody plants, most notably on ''Citrus'' and ''Pittosporum''. Originally described in 1878 from specimens collected in New Zealand a ...

which has spread around the world.

Life cycle

Female scale insects in more advanced families develop from the egg through a first

instar An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...

(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 holometabolous insects have a true pupa). 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. EB1911 Hemiptera - Fig

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 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.

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 Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote th ...

, a number of different forms of reproductive systems are employed, including

. 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. Drosicha_Lefroy

Many species have the XX-XO system where the female is

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectiv ...

and homogametic while the male is heterogametic and missing a sex chromosome. In some

Diaspididae Diaspididae is the largest family of scale insects with over 2650 described species in around 400 genera. As with all scale insects, the female produces a waxy protective scale beneath which it feeds on its host plant. Diaspidid scales are far mo ...

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 ''

''. 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- 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.

Ecology

Scale insects are an ancient group, having originated in the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

, the period in which

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants ...

s came to dominance among plants, with only a few groups species found on

gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμν ...

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). The parasite biologist Robert Poulin notes that the feeding behaviour of scale insects closely resembles that of

ectoparasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

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. For example, cochineal species are restricted to cactus hosts, and the gall-inducing '' Apiomorpha'' are restricted to ''

Eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as ...

''. 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'', the boreal ensign scale, is a species of scale insect in the family Ortheziidae. It is native to Europe and is found in the soil and amongst plant litter and mosses on the ground. Description The adult female is about ...

(''Newsteadia floccosa'') inhabits

plant litter Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constitue ...

. A Hawaiian mealybug '' Clavicoccus erinaceus'' that fed solely on the now critically endangered '' Abutilon sandwicense'' has gone extinct as has another species '' Phyllococcus oahuensis''. Several other monophagous scale insects, especially those on islands, are threatened by coextinction due to threats faced by their host plants. Most scale insects are herbivores, feeding on phloem sap drawn directly from the plant's vascular system, but a few species feed on fungal mats and

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

, such as some species in the genus ''

Newsteadia ''Newsteadia'' is a genus of ensign scale insects in the superfamily Coccoidea Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they compris ...

'' 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. Scale insects secrete a large quantity of sticky viscid fluid known as " honeydew". This includes sugars, amino acids and minerals, and is attractive to ants as well as acting as a substrate on which sooty mould can grow. The mould can reduce

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...

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. Formica fusca and mealy bugs

Scale insect in the genus '' Cryptostigma'' live inside the nests of neotropical ant species. Many tropical plants need ants to survive which in turn cultivate scale insects thus forming a

tripartite symbiosis Tripartite symbiosis is a type of symbiosis involving three species. This can include any combination of plants, animals, fungi, bacteria, or archaea, often in interkingdom symbiosis. Ants Fungus-growing ants Ants of Attini cultivate fun ...

. Some ants and scale insects have a 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. This provides a means for the mealybug to be dispersed widely. Species of '' Hippeococcus'' have long clinging legs with claws to grip the ''

Dolichoderus ''Dolichoderus'' is a genus of ants found worldwide. Taxonomy The ants of the Neotropical genus ''Monacis'' were revised in 1959 by Kempf. However, Brown in 1973 and G. C. Wheeler and J. Wheeler in 1973 and 1976 considered both ''Monacis'' and ...

'' 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. 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. Ladybug(india)

Scale insects have various natural enemies, and research in this field is largely directed at the species that are crop pests. 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. 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. Natural enemies include parasitoid wasps, mostly in the families Encyrtidae and

Eulophidae The Eulophidae are a large family of hymenopteran insects, with over 4,300 described species in some 300 genera. The family includes the genus ''Elasmus'', which used to be treated as a separate family, "Elasmidae", and is now treated as a subf ...

, and predatory beetles such as fungus weevils, ladybirds and sap beetles. 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 ''Cryptolaemus montrouzieri'', common name mealybug ladybird or mealybug destroyer, is a ladybird species. Etymology Étienne Mulsant described ''C. montrouzieri'', naming the new species after a Marist brother and missionary, Abbe Montrouz ...

'' is known as the "mealybug destroyer" because both adults and larvae feed on mealybugs and some soft scales. 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.

Significance

As pests

Many scale species are serious crop pests and are particularly problematic for their ability to evade

quarantine A quarantine is a restriction on the movement of people, animals and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have been ...

measures. In 1990, they caused around $5 billion of damage to crops in the United States. The waxy covering of many species of scale protects their adults effectively from contact insecticides, which are only effective against the first-instar

nymph A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ...

stage known as the ''crawler''. However, scales can often be controlled using

horticultural oil Horticultural oils or narrow range oils are lightweight oils, either petroleum or vegetable based. They are used in both horticulture and agriculture, where they are applied as a dilute spray on plant surfaces to control insects and mites. They are ...

s that suffocate them, systemic pesticides that poison the sap of the host plants, or by biological control agents such as tiny

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

wasps and ladybirds. Insecticidal soap may also be used against scales. One species, the cottony cushion scale, is a serious commercial pest on 65 families of woody plants, including ''

'' fruits. It has spread worldwide from Australia. File:Scale insect.jpg, Adult female

(''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 lopezi'', a highly effective biological control of the

cassava ''Manihot esculenta'', commonly called cassava (), manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America. Although a perennial plant, cassava is extensively cultivated ...

mealybug

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 cochineal insects that attack invasive species of prickly pear, which spread widely especially in

Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...

and Africa.

Products

Some types of scale insect are economically valuable for the substances they can yield under proper husbandry. Some, such as the

cochineal The cochineal ( , ; ''Dactylopius coccus'') is a scale insect in the suborder Sternorrhyncha, from which the natural dye carmine is derived. A primarily sessile parasite native to tropical and subtropical South America through North America ...

, kermes, lac,

Armenian cochineal The Armenian cochineal (''Porphyrophora hamelii''), also known as the Ararat cochineal or Ararat scale, is a scale insect indigenous to the Ararat plain and Aras (Araks) River valley in the Armenian Highlands and in Turkey. It was formerly us ...

, and

Polish cochineal Polish cochineal (''Porphyrophora polonica''), also known as Polish carmine scales, is a scale insect formerly used to produce a crimson dye of the same name, colloquially known as "Saint John's blood". The larvae of ''P. polonica'' are sessile ...

, have been used to produce red dyes for coloring foods and dyeing fabrics. Both the colour name "

" and the generic name ''Kermes'' are from Italian ''carmesi'' or ''cremesi'' for the dye used for Italian silk textiles, in turn from the Persian ''qirmizī'' (قرمز), meaning both the colour and the insect. The colour name " scarlet" is similarly derived from Arabic ''siklāt'', denoting extremely expensive luxury silks dyed red using kermes. Some waxy scale species in the genera ''

Ceroplastes ''Ceroplastes'' is a genus of wax scales in the family Coccidae The Coccidae are a family of scale insects belonging to the superfamily Coccoidea. They are commonly known as soft scales, wax scales or tortoise scales. The females are flat wit ...

'' and '' Ericerus'' produce materials such as

Chinese wax Chinese wax is a white to yellowish-white, gelatinous, crystalline water-insoluble substance obtained from the wax secreted by certain insects. It resembles spermaceti but is harder, more friable, and with a higher melting point. Two scale insects ...

, and several genera of

lac scale ''Kerriidae'' is a family of scale insects, commonly known as lac insects or lac scales. Some members of the genera ''Metatachardia'', ''Tachardiella'', ''Austrotacharidia'', ''Afrotachardina'', ''Tachardina'', and ''Kerria'' are raised for comme ...

s produce shellac. File:Indian collecting cochineal.jpg, Collecting scale insects from a prickly pear for a

dyestuff A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and ...

, cochineal, 1777 File:Weltliche Schatzkammer Wienc.jpg, Coronation cloak of King

Roger II of Sicily Roger II ( it, Ruggero II; 22 December 1095 – 26 February 1154) was King of Sicily and Africa, son of Roger I of Sicily and successor to his brother Simon. He began his rule as Count of Sicily in 1105, became Duke of Apulia and Calabria i ...

, 1133. Silk scarlet cloth dyed with 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

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. Scale insects are members of the Sternorrhyncha. The

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological s ...

of the extant groups, inferred from analysis of small subunit (18S)

ribosomal RNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from riboso ...

, is shown in the first cladogram. Acropyga glaesaria SMFBE457B2 01

Phylogenetic diversification within the Coccomorpha has been analysed by the taxonomist Isabelle Vea and the entomologist David Grimaldi in 2016, combining DNA (3 gene regions) and 174 morphological characters (to allow

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

evidence to be incorporated). They showed 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. The Coccomorpha appeared at the start of the

period, some 245 mya; the neococcoids some 185 mya. Scale insects are very well represented in the fossil record, being abundantly preserved in

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. In the cladogram below the genus ''Pityococcus'' is moved to the "Neococcoids". A cladogram showing the major families using this methodology is shown below. Recognition of scale insect families has fluctuated over time, and the validity of many remains in flux, with several recognized families not included in the phylogeny presented above including extinct groups are listed below: * Archecoccoidea ** Apticoccidae ** Arnoldidae ** Burmacoccidae ** Callipappidae ** Coelostomidiidae ** Electrococcidae ** Grimaldiellidae ** Grohnidae ** Hammanococcidae ** Jersicoccidae ** Kozariidae ** Kukaspididae **

Kuwaniidae Kuwaniidae is a family of scales and mealybugs in the order Hemiptera. There are at least 4 genera and about 14 described species in Kuwaniidae. Genera These four genera belong to the family Kuwaniidae: * ''Kuwania'' Cockerell, 1903 * ''Neogreen ...

** Labiococcidae ** Lebanococcidae ** Lithuanicoccidae ** Macrodrilidae ** Marchalinidae **

** Matsucoccidae ** Monophlebidae **

** Pennygullaniidae ** Phenacoleachiidae **

Pityococcidae Pityococcidae is a family of scales and mealybugs in the order Hemiptera Hemiptera (; ) is an order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, ...

** Putoidae ** Serafinidae ** Steingeliidae ** Stigmacoccidae ** Termitococcidae ** Weitschatidae ** Xylococcidae * Neococcoidea ** Aclerdidae ** Albicoccidae ** Asterolecaniidae **

Carayonemidae Carayonemidae is a family of scale insects commonly known as carayonemids. They typically live among mosses and leaf litter which is unusual for scale insects. Members of this family come from Neotropical areas of South and Central America. Life ...

Cerococcidae Cerococcidae is a family of scale insects commonly known as ornate pit scales or cerococcids. There are 83 species in 5 genera. Members of this family occur in all regions of the world. Description Adult females produce a protective waxy test ...

** Cissococcidae **

Coccidae The Coccidae are a family of scale insects belonging to the superfamily Coccoidea. They are commonly known as soft scales, wax scales or tortoise scales. The females are flat with elongated oval bodies and a smooth integument which may be covere ...

Conchaspididae Conchaspididae is a small family of scale insects known as false armoured scales because of their resemblance to Diaspididae (but not incorporating exuviae on their body). Description Members of the family Conchaspididae secrete a waxy scale, in ...

** Cryptococcidae ** Dactylopiidae **

** Eriococcoidae **

Halimococcidae Halimococcidae is a family of scale insects in the order Hemiptera. Members of the family are commonly known as pupillarial palm scales or halimococcids. Most species are found on the leaves of palm trees where they suck sap, but some species occ ...

** Hodgsonicoccidae ** Inkaidae ** Kermesidae ** Kerridae **

Lecanodiaspididae Lecanodiaspididae is a family of scale insects commonly known as false pit scales or lecanodiaspidids. Members of this family come from all parts of the world but are most numerous in the Far East.Micrococcidae ** Phoenicococcidae ** Porphyrophoridae ** Pseudococcidae ** Rhizoecidae ** Stictococcidae ** Tachardiidae

References

External links

ScaleNet homepage

* ttp://nlbif.eti.uva.nl/bis/diaspididae.php Diaspididae of the World
Scale Insect Forum

On the

University of Florida The University of Florida (Florida or UF) is a public land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...

Institute of Food and Agricultural Sciences The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is a teaching, research and Extension scientific organization focused on agriculture and natural resources. It is a partnership of federal, state, and county governmen ...

''Featured Creatures'' website:
''Ceroplastes rubens'', red wax scale

{{DEFAULTSORT:Scale Insect Sternorrhyncha Agricultural pest insects Insect pests of ornamental plants Insect pests of tropical forests Extant Triassic first appearances