Scales and Mealybugs

Pronunciation

How to pronounce Coccoidea: //kɒkˈɔɪdiə//

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Images

Summary

Coccoidea, or scale insects, are members of the Hemiptera order characterized by extreme sexual dimorphism and plant parasitism. Adult females are usually wingless and coated in wax, while males are typically small, winged, and ephemeral. They exhibit varied reproductive strategies and play significant roles in ecosystems, agriculture, and as sources of economically valuable products.

Physical Characteristics

Scale insects vary dramatically in appearance, from 1-2 mm small organisms beneath wax covers to shiny, pearl-like objects of about 5 mm. Adult females are often immobile and permanently attached to the plant they feed on, resembling scales, with soft bodies and no limbs for protection. Key characteristics include a single segmented tarsus with one claw at the tip. Adult males resemble slender aphids or small flies with legs and sometimes wings, typically with 5 segmented legs.

Identification Tips

Look for immobile, dome-shaped or waxy coverings on plants, indicating adult females. Males are winged and may resemble small flies but are rarely noticed. Check for a single segmented tarsus and absence of limbs in females as distinguishing features.

Habitat

Scale insects can inhabit a variety of habitats, predominantly associating with hosts such as trees and other plants. Some species have specific habitat requirements, such as damp meadows or forest litter.

Distribution

Approximately 8,400 species of scale insects are found worldwide, with around 1,100 species in ~250 genera across 28 families in various regions.

Diet

Scale insects are herbivores that feed on phloem sap by piercing plant tissues, drawing sap directly from the vascular system. Some species can also feed on fungal mats and fungi.

Life Cycle

The life cycle of scale insects typically includes an egg stage, a crawler stage (first instar), and subsequent instar stages before becoming adults. Female scale insects become largely immobile and remain attached to their food source, while males undergo several instar stages before emerging as brief, non-feeding adults.

Reproduction

Scale insects exhibit various reproductive strategies, including sexual reproduction, asexual reproduction through parthenogenesis, and hermaphroditism in some species. Some females produce offspring without mating, while males may eliminate paternal genetic material during development, leading to various sex determination systems.

Predators

Natural enemies include parasitoid wasps, predatory beetles (such as ladybirds and fungus weevils), and entomopathogenic fungi. Ladybirds are known to target both aphids and scale insects, while ants often protect scales from predators in exchange for honeydew.

Ecosystem Role

Scale insects can play significant roles in ecosystems as herbivores, influencing plant health and serving as food sources for predatory insects. Their mutualistic relationships with ants also contribute to ecosystem dynamics.

Economic Impact

Scale insects can be serious agricultural pests, contributing to substantial economic damage in crop production. Some species are valuable for producing dyes and lac, while others are used in biocontrol of invasive plant species.

Cultural Significance

Cochineal scale insects are historically significant for producing red dyes used in textiles and foods, leading to cultural and economic impacts in various regions.

Collecting Methods

• Aicide/Contact insecticide application during crawler stage
• Horticultural oils

Preservation Methods

• Mounting
• Alcohol preservation

Evolution

Scale insects are part of the infraorder Coccomorpha and originated around the time angiosperms diversified in the Cretaceous. Their phylogenetic relationships suggest they switched from gymnosperms to angiosperms during their evolution.

Similar Taxa

• Aphids
• Whiteflies
• Jumping plant lice

Misconceptions

Scale insects are often misunderstood as simple plant parasites rather than complex organisms with diverse reproductive strategies and mutualistic relationships with ants.

Tags

• Entomology
• Pest Control
• Biodiversity
• Conservation
• Insect Evolution