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Bug of the Month: Multicolored Asian lady beetle

side view of multicolored Asian lady beetleCommon name: Multicolored Asian lady beetle

Latin name: Harmonia axyridis

Taxonomy:
Kingdom Animalia
   Phylum Arthropoda
      Class Insecta
         Order Coleoptera
            Family Coccinellidae

 

Lady beetles in general

Lady beetles (Family Coccinellidae) go by many names, including ladybugs and ladybirds. Most lady beetles have a characteristic rounded, domed shape, and many have bright red, orange, or yellow coloring (often with black spots). The bright coloring serves as a warning to potential predators that the lady beetle tastes bad and contains defensive chemicals. As many gardeners know, most species of lady beetles are voracious predators themselves, both as adults and larvae, and prey on aphids and other soft-bodied insects like scale insects and mealybugs. Because they are such effective predators of garden and crop pests, lady beetles have often been used as “biocontrol” agents. In fact, many of our common lady beetles are species that were purposefully introduced to control aphids and other pests, and have since spread to other habitats. In some cases, however, the introduced lady beetles have taken on pest status themselves. For instance, their large numbers can displace native lady beetle species in their native habitats. There are close to 500 species of lady beetles in North America.

overhead view of the multicolored Asian lady beetleHow to identify multicolored Asian lady beetles

Multicolored Asian lady beetles have the typical shape of a lady beetle with smooth, rounded elytra (hind wings) and a small pronotum and head. (The pronotum is the visible segment between the head and the abdomen. The abdomen of a lady beetle is usually entirely covered by its wings.) They range in length from 5 to 8 mm (~1/4”). Their coloring is highly variable across individuals. The background color can be orange or red, and the number of black spots may vary from none to many (20+). The easiest way to identify this species is to look for the large black ‘M’ shape on the white pronotum.

Another common (and also introduced) lady beetle species found on the islands that could be confused with the multicolored Asian lady beetle is the seven-spotted lady beetle. As its name suggests, this beetle always has seven spots (3.5 on each wing), and it has much more black on the pronotum.

Where to find multicolored Asian lady beetles on the Boston Harbor Islands

Multicolored Asian lady beetles occur on all of the islands we have sampled, and most likely occur on all the islands where we have not yet looked. They are typically found on plants—both herbaceous and woody—where they may be resting or hunting for aphids and other prey.

How multicolored Asian lady beetles make a living

side by side comparison of 2 multicolored lady beetlesMulticolored Asian lady beetles mate in the spring. Their larvae go through four growth stages (instars) during the course of a couple of weeks, when they feed hungrily on aphids and other prey (including scale insects, mites, and thrips). They live as pupae for 5 or 6 days, and the emerging adults may live from several months to three years. Adults are also predators on aphids and other soft-bodied insects. Two or more generations may be produced during the growing season. In the autumn, when temperatures start to fall, multicolored Asian lady beetles aggregate into large swarms and seek out warm, dry over-wintering sites. In their native Asia, over-wintering sites are typically rocky cliffs at high elevations, but in North America, these lady beetles are attracted to light-colored buildings, where they typically gain entry through cracks in the wall. Once inside the building, huge numbers of lady beetles can become a nuisance to homeowners. An additional annoyance is their habit of exuding yellow, smelly fluid from their legs as a defense mechanism when disturbed.

comparison of different lady beetle species

Where in the world multicolored Asian lady beetles occur

As their name suggests, multicolored Asian lady beetles are native to Asia, including China and Japan. They were first introduced to North America in the early 1900s as a biocontrol agent, and many more intentional releases occurred after this, but it wasn’t until 1988 that a population of these lady beetles became established in Louisiana. Since then, here have been numerous additional introductions to various parts of the United States and the multicolored Asian lady beetle has spread throughout most of the U.S. and southern Canada. They have also been introduced to Europe and South America.

To learn more about multicolored Asian lady beetles (and lady beetles in general)

On the web:

In print:

    Gordon, R.D. 1985. The Coleoptera (Coccinellidae) of America north of Mexico. Journal of the New York Entomological Society. 93: 1–912.

    Marshall, S.A. 2006. Insects—their natural history and diversity: with a photographic guide to insects of eastern North America. Firefly Books, Buffalo NY.