Longhorned Beetles (Borers; Sawyer Beetles)

About 1,000 species in North America north of Mexico

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Red milkweed beetle eating a common milkweed leaf.
The red milkweed beetle (Tetraopes tetrophthalmus) specializes in eating milkweeds. The larvae bore into the roots, and the adults chew the foliage. The bright red is a warning: Like several other insects, this beetle ingests milkweed’s toxic chemicals and becomes unpalatable or sickening to predators.
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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Banded longhorn beetle on a wild rose
Banded Longhorn
The banded longhorn beetle (Typocerus velutinus) is in a group called flower longhorns. Note the rusty color, yellow bands, and black antennae. This is a common species.

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Red-headed ash borer on tree bark
Red-Headed Ash Borer
The larvae of red-headed ash borer (Neoclytus acuminatus) feed on a variety of dead or dying hardwoods, including oak, hickory, persimmon, hackberry, as well as ash. This helps the decomposition process and enriches the soil.

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Ivory-marked beetle crawling on bark
Ivory-Marked Beetle
The ivory-marked beetle (Eburia quadrigeminata) is a longhorned beetle whose larvae bore deep into the heartwood of a variety of deciduous trees, including oak, hickory, maple, cherry, ash, elm, and more. It can have a remarkably long lifespan: Adults have been known to emerge from finished furniture and flooring after 40 years.

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Locust borer on leaf
Locust Borer
The locust borer (Megacyllene robiniae) is a longhorned beetle whose larvae tunnel into the trunks of black locust (Robinia pseudoacacia). Their infestations often kill weakened or damaged black locusts. The colorful black and yellow adults are often seen in late summer as they feed on the pollen of goldenrod and other flowers.

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Red-femured milkweed borer beetle on milkweed leaf
Red-Femured Milkweed Borer (Red Milkweed Beetle)
The red-femured milkweed borer (Tetraopes femoratus) specializes in eating milkweeds. The larvae bore into the roots; the adults chew the foliage and leaves. The bright red is a warning: Like other insects that eat milkweeds, this beetle ingests milkweed’s toxic chemicals and becomes unpalatable or sickening to predators.

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Flat-faced longhorn beetle crawling on wood
Flat-Faced Longhorn
The larvae of this beetle ― the four-humped flat-faced longhorn (Acanthoderes quadrigibba) ― feed on hardwood that is quite rotten. They play an important role in enriching the soil.

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Elm borer beetle resting on rocks in a flower planter
Elm Borer
The elm borer is a longhorned beetle whose larvae bore galleries under the bark of elm trees. It is one of the insects that can transmit the fungus that causes Dutch elm disease.

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Asian longhorned beetle male, specimen
Asian Longhorned Beetle (Adult Male)
The invasive Asian longhorned beetle (ALB) is shiny black with white spots. The antennae are long and have alternating bands of black and white. The antennae are usually 1 to 2 times greater than the length of the body. The upper sections of the legs are whitish to blue.

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Asian longhorned beetle larva, held in someone's fingers
Asian Longhorned Beetle Larva
ALB larvae are yellowish-white, wormlike, cylindrical, and fleshy, with a varied texture on the underside. While young, larvae tunnel beneath the bark and feed on the inner bark of tree branches and trunk. As they grow, they tunnel deeper into the sapwood. The preferred trees of this invasive species include nearly all our maple species, as well as

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Photo of Asian longhorned beetle pupa inside gallery in wood
Asian Longhorned Beetle Pupa
The pupae of Asian longhorned beetles are off-white to light brown and resemble an immature version of the adult with legs and antennae compressed against the body. The Asian longhorned beetle was most likely transported to the United States as pupae and larvae hidden within the wood of pallets and crates.
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. They are 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, over great periods of time, caused trees to be strong and resistant to such onslaught.