''Aspidiotus destructor'', the coconut scale, is a species of
armoured scale insect in the family
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 ...
,
found in many tropical and subtropical parts of the world. It is a serious pest of
coconut and
banana, and attacks a range of other fruiting trees and ornamental plants.
Description
All but the 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 ...
nymphs
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 ...
live under the protection of a waxy
test
Test(s), testing, or TEST may refer to:
* Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities
Arts and entertainment
* ''Test'' (2013 film), an American film
* ''Test'' (2014 film), ...
or scale and remain in one place. First instar nymphs have legs and move about looking for somewhere to settle. Second instar and adult females have rounded, flattish tests up to in diameter. They have no eyes or appendages, and their soft yellow bodies are visible through the translucent test, giving them the appearance of miniature fried eggs. Males have smaller, more elongated tests, and pass through a
pseudo-pupal stage before
metamorphosing into reddish, gnat-like insects with eyes, antennae, legs and wings, but no mouthparts.
[
]
Distribution
''Aspidiotus destructor'' has a global distribution in tropical and subtropical regions. It is believed to have originated in South Asia but has spread to other parts of Asia, Australia, Africa, Brazil, Central America, the Caribbean region and North America. Its accidental introduction to various Pacific Islands where it lacked natural enemies caused much crop loss.
Hosts
''Aspidiotus destructor'' is a major pest of coconut, but also feeds on various fruit trees and ornamental plants; these include banana, apple, avocado, breadfruit, citrus, grape, guava, mango, ficus, camellia, papaya, ginger, bird of paradise, sugarcane, plumeria and oil palms. On coconut it infests the under surface of the leaves, the leaf stalks, flowers and small fruit, causing discolouration, chlorosis and distortion.[
]
Life cycle
Mature females lay a batch of up to about 65 eggs over a ten-day period, retaining them under the test. When first hatched, the nymphs are known as "crawlers" and move to other parts of the plant before settling. Having moulted, they start sucking sap from the host plant; females will remain static for the rest of their lives, but males will become mobile after their final moult. Mature females release a pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
to attract males. A female will lay several batches of eggs before dying, but adult males do not feed and soon die.[
]
Biological control
''Aspidiotus destructor'' was causing severe damage to both coconuts and bananas on Guam
Guam (; ch, Guåhan ) is an organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. It is the westernmost point and territory of the United States (reckoned from the geographic cent ...
in the early 1900s. Several parasites and predators were introduced in an attempt to control the scale without much success, until the coconut scale predator (''Cryptognatha nodiceps'') was introduced from Trinidad and successfully controlled the pest within nine months.[ This ]lady beetle
Coccinellidae () is a widespread family of small beetles ranging in size from . They are commonly known as ladybugs in North America and ladybirds in Great Britain. Some entomologists prefer the names ladybird beetles or lady beetles as they ...
was successful where the other predators had failed because of its voracious appetite, its fecundity, and its ability to seek out and feed on other prey species when the scale population diminished.Príncipe
Príncipe is the smaller, northern major island of the country of São Tomé and Príncipe lying off the west coast of Africa in the Gulf of Guinea. It has an area of (including offshore islets) and a population of 7,324 at the 2012 Census; in West Africa in the 1950s, but other species of lady beetle have been more effective in Mauritius
Mauritius ( ; french: Maurice, link=no ; mfe, label= Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It ...
and the New Hebrides
New Hebrides, officially the New Hebrides Condominium (french: link=no, Condominium des Nouvelles-Hébrides, "Condominium of the New Hebrides") and named after the Hebrides Scottish archipelago, was the colonial name for the island group ...
.[
]
References
Further reading
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{{Taxonbar, from=Q10420240
Insects described in 1869
Aspidiotina