Asian Long Horned Beetle

The Asian longhorned beetle, Anoplophora glabripennis, is a large black-and-white beetle with extremely long antennae. It comes from China and Korea, where it is sometimes called the starry sky beetle because of the white spots on its shiny black back. Outside its home range it is a serious invasive pest that can kill healthy hardwood trees.

Asian longhorned beetle Quick Facts

Common name	Asian longhorned beetle
Scientific name	Anoplophora glabripennis
Kingdom	Animalia
Phylum	Arthropoda
Class	Insecta
Order	Coleoptera
Family	Cerambycidae
Genus	Anoplophora
Type	Insect (longhorn beetle)
Diet	Larvae eat the wood of living hardwood trees; adults eat leaves and twig bark
Habitat	Hardwood forests, parks, streets and gardens
Native range	China and Korea
Size	About 2-4 cm long, plus very long antennae
Colours	Shiny black with white spots; black-and-white banded antennae
Special feature	Invasive pest that can kill healthy trees

This beetle has been carried by accident to North America and Europe, hidden inside wooden pallets and packing crates. Wherever it turns up, people work hard to stop it from spreading.

What It Looks Like

Adult Asian longhorned beetles are big, about 2 to 4 cm long (roughly 1 to 1.5 inches), not counting the antennae. The body is glossy black, with up to about 20 irregular white spots on each wing cover.

The antennae are the most striking feature. They have black-and-white bands and can be 1.5 to 2.5 times as long as the body, and the male’s are the longest. The legs and feet often have a pale bluish-white tinge.

Asian longhorned beetles can fly, but they are fairly heavy and usually fly only short distances, often staying on the same tree or moving to one nearby. That is why moving infested wood is the main way they spread.

Where It Lives

In its native range in eastern Asia, this long-horned beetle lives in forests, city streets and tree plantations. It was first discovered in the United States in New York in 1996, and later in Chicago, New Jersey, Massachusetts, Ohio and other places. It has also been found in Canada and in several European countries, including Austria, France, Germany, Italy and the United Kingdom.

Unlike many wood-boring insects, the Asian longhorned beetle attacks healthy trees, not just weak or dying ones. Its favorite trees are maples, but it also attacks horse chestnut, birch, willow, poplar, elm and many other hardwood trees. Trees along streets, in parks and in back yards are all at risk.

What It Eats

Adult beetles feed on leaves, leaf stalks and the bark of small twigs. This feeding does only minor damage.

The larvae are the real problem. They feed inside the tree, first on the living layer just under the bark (the cambium), and then they tunnel deep into the wood. This cuts off the flow of water and nutrients through the tree.

Life Cycle

The Asian longhorned beetle goes through complete metamorphosis: egg, larva, pupa and adult. The whole cycle usually takes one to two years, depending on the climate and the kind of tree.

In summer, the female chews a small pit in the bark and lays a single egg in it. She repeats this many times, laying dozens of eggs over her life. Before she starts laying, she spends some days feeding to mature.

The eggs hatch into creamy white, legless grubs. They feed under the bark, then bore into the heartwood, pushing sawdust-like waste called frass out of the tunnels. Larvae can spend the winter inside the tree in a resting state. When fully grown, a larva turns into a pupa near the end of its tunnel.

The new adult chews its way out through a perfectly round exit hole, usually in summer. In the Northern Hemisphere, adults are most often seen from about July to October.

Mating

When a male finds a female on a tree, he touches her with his antennae. If she is ready to mate, the pair may stay together for some time while the male guards her from other males. If she is not, she may kick, run, fly away or drop to the ground.

Damage

Asian longhorned beetles can kill healthy trees. Larval tunnels weaken trunks and branches so they may break and fall, and open wounds let fungi and disease get in. An infested tree usually takes several years to die, but there is no way to save it once the beetles are inside.

Because maples and other trees are so important for forests, cities, wildlife and the maple syrup industry, this beetle is considered one of the most dangerous invasive forest insects in North America. Programs to find and remove it have cost many millions of dollars.

Signs of an Infestation

Look for these signs on maples and other hardwood trees, especially in summer:

• Perfectly round exit holes about 3/8 inch (10 mm) across, or larger, about the size of a pencil or bigger.
• Small, oval or round pits chewed in the bark, where eggs were laid.
• Sap oozing from the bark.
• Coarse sawdust (frass) piled at the base of the tree or in branch forks.
• Dead branches or leaves turning yellow early, even when there has been no drought.
• The large black-and-white beetles themselves.

How to Help Stop It

There is no simple treatment you can do at home, but you can play an important part:

• Report it. If you think you have seen an Asian longhorned beetle, take a photo, note where it was and contact your local plant health or forestry authority.
• Don’t move firewood. Buy or gather firewood near where you will burn it, or use certified heat-treated wood.
• Follow quarantine rules in areas where the beetle has been found.

When the beetle is found, experts survey the area and remove infested trees, then chip or burn the wood so no larvae survive. This approach has wiped out the beetle from several places, including Chicago and Toronto.

Related: Locust Trees

Asian longhorned beetle FAQs