Diaspididae

Armored Scale Insects, Armored Scales, Hard Scales

Genus Guides

is the largest of scale insects, comprising over 2,650 described in approximately 400 . Members are commonly known as insects due to their distinctive protective covering, which incorporates from the first two nymphal instars, sometimes with fecal matter and plant fragments. The female remains permanently beneath this armor, feeding on host plant tissues through . The family includes numerous economically significant pests such as the California red scale (Aonidiella aurantii), San Jose (Diaspidiotus perniciosus), and gloomy scale (Melanaspis tenebricosa), which damage crops, ornamentals, and forest trees worldwide.

Aulacaspis yasumatsui by (c) Lic. Kevin Miguel Garibaldi Fierro, some rights reserved (CC BY), uploaded by Lic. Kevin Miguel Garibaldi Fierro. Used under a CC-BY license.

Lindingaspis by (c) Grey Smith, some rights reserved (CC BY), uploaded by Grey Smith. Used under a CC-BY license.

Lindingaspis by (c) Jon Sullivan, some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Diaspididae: //ˌdaɪəˈspɪdɪdiː//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from other insect by the female's hard, separable armor (test) that is not to the body and can be lifted to reveal the insect beneath. The test is constructed from wax secretions combined with cast skins from the first two nymphal instars, creating a durable, often circular or elongate structure. Unlike soft scales (Coccidae), do not produce honeydew and lack the convex, waxy coating typical of that family. The female is apodous and under the test, while males develop into small, winged, gnat-like with reduced mouthparts.

Images

Habitat

Found on virtually all vascular plants including trees, shrubs, and woody vines. Inhabits bark, leaves, needles, and fruits depending on . Many species thrive in urban and agricultural environments where plants are abundant. Some species occupy specialized : pine needle scales (Chionaspis spp.) on conifer foliage, oystershell scale (Lepidosaphes ulmi) on deciduous tree bark, and palm scales on tropical ornamentals.

Distribution

distribution with highest diversity in tropical and subtropical regions. Native and introduced occur across all continents except Antarctica. Particularly diverse in the Oriental and Australasian regions. have established in temperate zones through human-mediated transport of plant material, with significant pest problems in California, Florida, the southeastern United States, Mediterranean Europe, and other regions with intensive horticulture.

Seasonality

Activity patterns vary by and climate. In temperate regions, most species overwinter as or mated females beneath the armor. typically occurs in spring when plants resume growth, with one to multiple per year depending on species and latitude. Some species like gloomy (Melanaspis tenebricosa) reach higher densities and have extended activity periods in urban heat islands. Tropical and greenhouse may reproduce continuously without .

Diet

Phloem-feeding; all life stages except males insert stylets into plant tissues to extract sap. Feeding occurs intracellularly rather than in vascular tissues, which renders less effective than against soft scales.

Life Cycle

Females reproduce oviparously or ovoviviparously, depositing or live young beneath the protective test. First-instar nymphs () are the only mobile female stage, dispersing to find feeding sites on new growth or other plants. After settling, crawlers and lose their legs, becoming permanently . The second molt produces the female or, in males, a prepupal stage. Males develop through four instars, emerging as winged adults that seek sessile females for mating. The female armor incorporates from the first two molts.

Behavior

Females are entirely sedentary after the stage, remaining fixed beneath their constructed armor for life. Crawlers disperse actively by , or passively via wind, birds, mammals, insects, or human activity. Males are short-lived, non-feeding, and fly to locate females. Some exhibit . African species attended by Melissotarsus ants are completely denuded of their armor, with ants consuming the protective covering while maintaining hidden nests under tree bark.

Ecological Role

Herbivores that can reach damaging densities on plants, causing direct injury through sap removal and indirect effects via stress and entry points. Serve as prey for diverse natural enemies including lady beetles (Chilocorus, Rhyzobius), lacewings, predatory , predatory mites, and (especially Aphelinidae such as Aphytis and Encarsia ). Some species function as engineers by altering plant resource allocation, though primarily considered pests in managed systems.

Human Relevance

Major agricultural and horticultural pests causing billions of dollars in damage and control costs annually. Notable pests include California red scale threatening citrus, San Jose attacking deciduous fruit trees, oystershell scale damaging orchards and ornamentals, and cycad aulacaspis scale endangering conservation plantings. are increasing with global trade, requiring intensive , detection, and management efforts. using has been historically successful, as with the vedalia beetle and Aphytis . Management relies on monitoring , applications, and conservation of natural enemies.

Similar Taxa

Coccidae (soft scales)Soft scales have convex, waxy bodies often coated with powdery or cottony wax, produce honeydew, and lack the hard, constructed armor of . Their tests are integral to the body, not separable.
Pseudococcidae (mealybugs)Mealybugs are mobile throughout life, covered with fluffy white wax filaments, and retain legs in all instars. females become and legless with a hard, non-filamentous armor.
Monophlebidae (giant scales)Giant scales are larger, often with prominent waxy ovisacs, and have more visible body segmentation. are generally smaller with the distinctive constructed test incorporating .