Scale insect
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| Missing image Wax_scale.jpg Scale insect Wax scales on a lemon tree branch | ||||||||||||||||||||
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Aclerdidae |
The scale insects are small insects of the order Hemiptera, generally classified as the superfamily Coccoidea. There are over 7,000 species of scale insect.
Scale insects are all parasites of plants, feeding on sap drawn directly from the plant's vascular system. Adult scales are immobile and permanently attached to the plant they have parasitized. They secrete a waxy coating for defense; this coating causes them to resemble reptilian scales, hence the name.
Scale insects feed on a wide variety of plants, and the majority of scale species are considered pests. Some types are economically valuable, such as the cochineal scales and lac scales. Scale insects' waxy covering makes them quite resistant to pesticides, which are only effective against the juvenile crawler stage. However, scale can be controlled with horticultural oil, which suffocates them, or through biological controls. Soapy water is also reported to be effective against infestations of houseplants.
Female scale insects, unusually for hemiptera, retain their larval form at sexual maturity. Adult males have wings but never feed and die within a day or two. The specifics of their reproductive systems vary considerably within the group, including hermaphroditism and seven forms of parthenogenesis.
External links
- ScaleNet homepage (http://www.sel.barc.usda.gov/scalenet/scalenet.htm)
- Cottony Cushion Scale: the pest that launched a pest control revolution (http://gardenbees.com/biological%20control/revolution.htm) with photosTemplate:Invert-stub