Armored Scales

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Rank & taxon

Family Diaspididae

Family

Family Diaspididae

Description

Mature females can be 1-3.5 mm in length, but most are 1.5-2 mm long. Adult females secrete a waxy coating that functions like a suit of armor; it may be circular to pyriform to elongate in shape, reflecting the form of the insect inside. They may be white, yellow, purple, red, or orange in color. The protective coating is not a part of the body and can be removed. All stages of armored scale insects are legless with the exception of the first-instar crawlers and the third, fourth, and adult male. The crawlers are very small, oval and flattened in form, with very short but functional legs.

Distribution

Worldwide; 400 genera, representing over 2,650 described species

Biology/life cycle

Life cycles vary among species. Females may lay eggs or give birth to live young under the scale cover. The first instar, or crawler stage, emerges from the cover through a small posterior opening and may disperse either passively by wind or actively by walking. Females have 3 instars while males have 5 instars which include two "pupal" instars. The female scale cover is formed through the incorporation of the first- and second-instar skins as they are shed, while males only incorporate the shed exuviae of the crawler stage. The family encompasses a variety of life histories; there may be 1 to 6 generations per year, and overwintering may occur in any instar except the third, fourth, or adult male.

Hosts

Palms: a wide variety of palms

Other: a wide variety of species, but generally found on long lived species such as trees and shrubs.

Representative taxa on palms

Aspidiotus destructor, the coconut scale insect, is a flat, circular, transparent scale commonly found on coconut palms but also occurs frequently on other palm species.

Ischnaspis longistoris, the black-thread scale insect, has a distinctive body form in the female, with a shiny, black, and extremely long and narrow scale cover. This species is one of the most frequently encountered armored scales on a variety of decorative palms, and it thrives under greenhouse conditions.

Additional comments

Armored scales do not secrete honeydew, but are still occasionally associated with ants. They may be found on nearly any part of the plant, though they are rarely found on roots. Armored scales are one of the most commonly encountered insect pests on cultivated palms. The scale covers often persist on the plant long after the insect itself has expired. Definitive species identification in armored scales is usually based on microscopic characters from a slide-mounted adult female, and should be done by an expert.

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