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The '''scale insects''' are small [[insect]]s of the order [[Hemiptera]], generally classified as the superfamily '''Coccoidea'''. There are about 8,000 species of scale insects.
Most scale insects are [[parasite]]s of [[plant]]s, feeding on [[sap]] drawn directly from the plant's vascular system. A few species feed on fungal mats and [[fungi]], e.g., some species in the genus ''Newsteadia'' in the family Ortheziidae. Scale insects vary dramatically in their appearance from very small organisms (1–2 mm) that occur under wax covers (some look like oyster shells), to shiny pearl-like objects (about 5 mm), to creatures covered with mealy wax. Adult female scales are almost always immobile (aside from [[mealybug]]s) and permanently attached to the plant they have parasitized. They secrete a waxy coating for defense; this coating causes them to resemble reptilian scales or fish scales, hence the name.
Scale insects feed on a wide variety of [[plant]]s, and many scale species are considered [[pest (animal)|pest]]s. Some types are economically valuable, such as the [[cochineal]], [[Polish cochineal]] and [[lac scale]]s. Scale insects' waxy covering makes them quite resistant to [[pesticide]]s, which are only effective against the first-instar nymph ''crawler'' stage. However, scales are often controlled with [[horticultural oil]]s, which suffocate them, or through [[biological control]].
Female scale insects, unusually for Hemiptera, retain the immature external morphology at sexual maturity. Adult males have wings but never feed and die within a day or two. Male scale insects are unusual in possessing only one pair of wings, thus making them resemble true flies ([http://en.wikipedia.org/wiki/Diptera Diptera]), though they lack the halteres (rudimentary hind wings) seen in flies, and have tail filaments, which do not occur in flies. The specifics of their reproductive systems vary considerably within the group, including hermaphroditism and at least seven forms of parthenogenesis.
<gallery>
Image:Scale insect.jpg| A female [[cottony cushion scale]], (''Icerya purchasi'' Maskell) scale with young crawlers
Image:Wax scale.jpg| Wax scales on a [[lemon]] tree branch
Image:Scale1.jpg| Scale insect under a [[Laurus nobilis|laurel]] leaf
</gallery>
==Major families==
Superfamily Coccoidea (scale insects)
* [[Icerya purchasi|cottony cushion scales]], giant coccids, and ground pearls ([[Margarodidae]])
* [[armored scale]] (Diaspididae)
* [[cochineal]] (Dactylopiidae)
* [[lac scale]]s (Kerriidae, Lacciferidae)
* [[soft scale]]s (Coccidae)
* [[pit scale]]s (Asterolecaniidae)
* [[mealybug]]s (Pseudococcidae)
* [[felted scale]]s (Eriococcidae)
==Attribution==
Much of this article is copied from http://en.wikipedia.org/wiki/Scale_insect under the Creative Commons Attribution-ShareAlike License ([http://en.wikipedia.org/w/index.php?title=Scale_insect&action=history authors])
== External links ==
{{wikispecies|Coccoidea}}
* [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] ''with photos''
* [http://nlbif.eti.uva.nl/bis/diaspididae.php Diaspididae of the World]
*[[Pests & Diseases of Roses]]
*[http://www.agri.gov.il/en/pages/10.aspx Scale Insect Forum]
*[http://entomology.ifas.ufl.edu/fasulo/woodypest/scales.htm Scales of southerastern U.S. woody ornamentals]
on the [[University of Florida|UF]] / [[Institute of Food and Agricultural Sciences|IFAS]] Featured Creatures Web site
*[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]
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{{DEFAULTSORT:Scale Insect}}
[[Category:Hemiptera]]
[[Category:Scale insects| ]]
[[Category:Agricultural pest insects]]
[[ca:Cotxinilla]]
[[cs:Červci]]
[[de:Schildläuse]]
[[es:Coccoidea]]
[[eo:Koĉo]]
[[fr:Coccoidea]]
[[hr:Štitaste uši]]
[[it:Coccoidea]]
[[he:כנימות מגן]]
[[la:Coccoidea]]
[[lt:Skydamariniai]]
[[hu:Pajzstetvek]]
[[nl:Schildluizen]]
[[ja:カイガラムシ]]
[[no:Skjoldlus]]
[[nn:Skjoldlus]]
[[pl:Czerwce]]
[[pt:Coccoidea]]
[[qu:Wallqanqacha usa]]
[[ru:Червецы]]
[[sl:Kaparji]]
[[sr:Штитасте ваши]]
[[sh:Štitaste uši]]
[[sv:Sköldlöss]]