Hosts or Prey
Plant-feeding spider mites (family Tetranychidae)
Identification
The adult spider mite destroyer is a lady beetle, sometimes called a ladybug or ladybird beetle. It is black and about 1/16 inch (1.5 mm) long. It can appear grayish because adults have a finely pitted surface covered with minute, pale hairs. The adult is dome-shaped (convex) on top, flat on bottom, and oval when viewed from above.
The eggs are oval and about 1/64 inch (0.4 mm) long. They are pale yellow to white when laid then turn gray and become blackish before hatching.
The larva is oblong and dark brown to gray when young. It is covered with numerous, minute, branched hairs. As the larva matures it becomes reddish, at first on the edges of the body; just prior to pupation the entire larva turns reddish.
Pupae are oblong or oval when viewed from above and flattened when viewed from the side. They are covered with tiny, pale hairs and depending on maturity vary in color from black to brown, gray, or reddish.
Life Cycle
Lady beetles develop through 4 life stages: egg, larva, pupa, and adult. Adult females lay eggs singly, scattered among spider mite colonies. Females typically lay about 100 to 200 eggs during their lifespan of 1 to 2 months. After hatching from an egg, Stethorus larvae develop through 4 increasingly larger instars. During warm temperatures the spider mite destroyer can complete egg to adult development in 3 to 4 weeks.
Habitat
Spider mite destroyers are specialized predators, feeding on all stages of spider mites. Stethorus adults and larvae each can consume up to 75 mites per day. Once mite populations have developed to moderate levels, Stethorus is especially important in reducing their abundance. Adult Stethorus readily fly and are highly effective at finding where mites are abundant, and then laying eggs there and voraciously feeding on the mites.
Stethorus eggs are laid singly on their sides and adhere tightly to the leaf. Females lay 1 to 10 eggs per leaf, depending on mite density. Most Stethorus eggs are laid on the underside of the leaf, alongside major veins.
Species
Seven or more Stethorus species occur in the United States. They are all predators of spider mites. The most common are Stethorus picipes, sometimes called Stethorus punctum picipes, in California and Stethorus punctum punctum in the Eastern United States, both of which are commonly called spider mite destroyer. Stethorus picipes is the only Stethorus species reported in California.
More Information
- The Coccinellidae (Coleoptera) of America North of Mexico, Journal of the New York Entomological Society
- Natural Enemies Handbook, UC Integrated Pest Management Program
- Protecting Natural Enemies and Pollinators, UC Integrated Pest Management Program
- A Revision of the New World Species of Stethorus Weise (Coleoptera: Coccinellidae), Transactions of the American Entomological Society
- Stethorus punctillum (Coleoptera: Coccinellidae), Cornell University
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Coleoptera
- Family: Coccinellidae
