Predatory Beetles : Mite-eating lady and Scymnus beetles

categories: Natural Enemies Predatory Beetles

last review date: 2025-08-23 07:30

Biology

The mite-eating lady beetles (Stethorus picipes, Stethorus punctillum) are pin head-sized (1/25 to 1/16 inch), black, oval, convex, and shiny, covered with sparse, fine, yellowish-to-white hairs.

Stethorus picipes (a native species) is most commonly found but S. punctillum (exotic) also occurs. Both species are voracious spider mite feeders, consuming 50 to 75 mites per day.

Overwintering occurs as non-reproductive adults in protected habitats (e.g., in ground debris, under bark). Adults emerge from hibernation sites in March-April, and seek out spider mite colonies, which they are able to do extraordinarily well.

Once found, females feed and lay eggs (approximately 15 eggs per day), rapidly exterminating small colonies of mites. Larvae develop through four instars, pupating after 12 days. Development from egg to adult takes approximately three weeks and three to four generations are produced during spring-summer.

Adults live for four to eight weeks during summer and thrive at temperatures between 68 and 95ºF.

A number of Scymnus beetles (Scymnus spp.) occur in Washington and all are predators of rust and spider mites as well as leafhoppers and mealybugs.

Slightly larger and similarly colored to Stethorus spp., they are easy to mistake for mite-eating lady beetles. However, their larvae are very different being white or pale colored with long thick cottony filaments adorning the body. They look a little like mealybugs and can be mistaken for this pest.

There are about 90 species of lady beetles in the Pacific Northwest. The five species most likely to be seen in Washington gardens include the transverse, convergent, seven-spot, multi-colored and mite-eating lady beetles.

Prey or Pest Targeted

• Lady beetles are industrious predators of not only aphids but also many other soft bodied arthropods like mites, thrips, insect eggs, scale insects and mealybugs.

Attracting and Keeping Natural Enemies
and Pollinators in Your Yard and Garden

• Native plants provide essential resources.
• Native flora also provides natural overwintering sites.
• Natural dispersion from nearby habitats ensures visitation.
• Some kinds of beneficial insects predatory mites are commercially available.
• Avoid regular use of synthetic, broad-spectrum pesticides.
• Infrequent use of certain narrow-spectrum pesticides is more compatible with some beneficials.
• Extensive lawns are also not conducive to attracting beneficial insects.

Management Options

See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• None recommended