Longhorned Beetles (Borers; Sawyer Beetles)

About 1,000 species in North America north of Mexico

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Photo of a red milkweed beetle eating a common milkweed leaf.
The red milkweed beetle (Tetraopes tetrophthalmus) specializes in eating milkweeds.
Family

Cerambycidae (longhorned beetles) in the order Coleoptera (beetles)

Description

Longhorned beetles are elongated and cylindrical, with antennae that are at least half the length of the body—sometimes much longer. There are many different species in this family. Often they are smooth, streamlined, and taper toward the back. Many are drab black, gray, or brown, while others mimic wasps with banded patterns of black and yellow or orange or have other colors.

The larvae are pale and grublike and are found inside wood or other plants.

Size

Length: from 1/8 to 2½ inches; many are about ½ inch (varies with species; does not include appendages).

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image of Banded Longhorn on a wild rose
Banded Longhorn
Click on photo to see slideshow.

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Photo of red-femured milkweed borer beetle on milkweed leaf
Red-Femured Milkweed Borer (Red Milkweed Beetle)

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image of Flat-Faced Longhorn Beetle crawling on wood
Flat-Faced Longhorn

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image of Ivory-Marked Beetle crawling on bark
Ivory-Marked Beetle

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image of Locust Borer on leaf
Locust Borer

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image of Red-Headed Ash Borer on tree
Red-Headed Ash Borer

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Photo of an Asian longhorned beetle male, specimen
Asian Longhorned Beetle (Adult Male)

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Photo of an Asian longhorned beetle larva, held in someone's fingers
Asian Longhorned Beetle Larva

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Photo of Asian longhorned beetle pupa inside gallery in wood
Asian Longhorned Beetle Pupa
Habitat and conservation

Each species of this large and diverse group of beetles is usually found near its special type of host tree, host plant, or dead wood. Since most adults can fly, they may be found almost anywhere. Some are attracted to lights. Adults of some types eat flowers and can be found on goldenrods or other plants. The larvae are usually found in dead, sick, or living trees. Some feed under the bark, where a tree’s vascular tissues are concentrated. Others bore deep into the trunk or roots.

Foods

The larvae of most species eat wood, living inside their tree. Most bore into dead, dying, or rotting wood, but others target living trees. Some of the latter are called girdlers, for they tunnel just under the bark of limbs, severing (girdling) the limb’s vascular system and killing the limb, whose dying tissues they feed on. Other species live in soil and eat roots. Adults eat various foods, including flowers, leaves, bark, fungi, and sap. Some adults only take water.

image of Longhorned Beetles Borers Sawyer Beetles Distribution Map
Distribution in Missouri

Statewide.

Status

Common. Economically important for the damage they cause to untreated wood products. Some species damage orchard, ornamental, or landscaping trees or other plants. The exotic, invasive Asian longhorned beetle is present in some parts of North America and could arrive in Missouri at any time. It could destroy millions of acres of hardwoods, including maples, elms, willows, and birches.

Life cycle

Lifespans range from a few months to decades, but most live 1–3 years. After mating, females seek out the appropriate food plant, usually a tree, in the appropriate stage of life, sickness, or decomposition, and deposit eggs into the wood. The larvae hatch and burrow into the tree, eating it and making tunnels in the process. Most of the longhorn’s life is spent in the larval stages. After pupating, adult beetles chew their way out of the wood and seek mates to continue the cycle.

Human connections

Although some species can damage living trees, our native longhorned beetles have a valuable place in the balance of nature. Humans, however, have imported exotic species that pose great danger to our forests. Never transport firewood. Learn to identify and report the presence of invasive species.

Ecosystem connections

Apart from the grave problem of exotic invasive beetles, our native longhorns are an important part of forest ecosystems. Their burrowing into dead or dying wood helps recycle nutrients into the soil. Also, wood-chewing insects have caused trees to be strong and resistant to such onslaught.