Red milkweed beetle

(Tetraopes tetrophthalmus)

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Conservation • Description • Habitat • Ecology • Distribution • Taxonomy

red milkweed beetle - Featured photo — Photo by Alfredo Colon

Conservation Status

IUCN Red List

not listed

NatureServe

NNR - Unranked

Minnesota

not listed

Description

Red milkweed beetle is one of three eastern milkweed longhorn beetles.

The female is 5 ⁄16″ to ⅝″ long, slightly larger than the male. The body is robust and has broad shoulders. The head, the plate covering the first segment of the thorax (pronotum), and the hardened wing covers (elytra) are red.

The face is nearly flat. The antennae are ½″ to ⅝″ long, about as long as the body. They are all black, not ringed with white or gray. The red base of the antennae is inserted into the black eye, splitting the eye into two parts. Two segmented feeler-like structures (palpi) are attached to the lower jaw-like structures (maxillae). The last segment of each maxillary palp is pointed.

The pronotum has four small black spots and a raised, disk-shaped hump.

Each elytron has five black spots: one in the shoulder region (humerus); a small spot at the base of the elytron near the scutellum; a small antemedial spot neat the suture; a large medial spot near the center; and a small post medial spot near the center.

The legs, including the third segments (femurs), are all black. The forward, middle, and back legs each have 5 end segments (tarsi). They appear as 4 segments because the minute fourth segment is concealed by the enlarged thirrd segment.

Size

Total length: 5 ⁄16″ to ⅝″

Similar Species

Red-femured milkweed borer (Tetraopes femoratus), as its name suggests, has red femurs. The antennae are ringed with white. The medial black spots on the elytra are no larger than other spots or are absent. It feeds exclusively on showy milkweed.

Habitat and Hosts

Meadows, fields, prairies, roadsides. Anywhere the host plants are found.

Milkweeds (Asclepias spp,)

Ecology

Season

May to September

Behavior

Life Cycle

Adults emerge in May or later, coinciding with the flowering of common milkweed. In early summer the female lays eggs near the base of a common milkweed stem. When the larvae hatch they bore into the stem. They overwinter in the roots.

Larva Food

Roots of common milkweed and possibly one or more other milkweed species.

Adult Food

Leaves and buds of common milkweed and possibly one or more other milkweed species.

Distribution

Sources

7, 24, 27, 30, 82, 83.

Biodiversity occurrence data published by: Minnesota Biodiversity Atlas (accessed through the Minnesota Biodiversity Atlas Portal, bellatlas.umn.edu. Accessed 10/20/2026).

Tetraopes tetrophthalmus (Forster, 1771) in Bánki, O., Roskov, Y., Döring, M., Ower, G., Hernández Robles, D. R., Plata Corredor, C. A., Stjernegaard Jeppesen, T., Örn, A., Pape, T., Hobern, D., Garnett, S., Little, H., DeWalt, R. E., Miller, J., Orrell, T., Aalbu, R., Abbott, J., Abreu, C., Acero P, A., et al. (2026). Catalogue of Life (2026-08-26 XR). Catalogue of Life Foundation, Amsterdam, Netherlands. https://doi.org/10.48580/dgyy9

Occurrence

Common

Taxonomy

Order

Coleoptera (Beetles)

Suborder

Polyphaga (Water, Rove, Scarab, Long-horned, Leaf, and Snout Beetles)

Infraorder

Cucujiformia

Superfamily

Cerambycoidea (Longhorn Beetles and Allies)

Family

Cerambycidae (Longhorn Beetles)

Subfamily

Lamiinae (Flat-faced Longhorn Beetles)

Tribe

Tetraopini

Genus

Tetraopes (Milkweed Longhorn Beetles)

Subordinate Taxa

Synonyms

Cerambyx tetrophthalmus

Cerambyx tornator

Lamia 13-punctata

Lamia fornator

Lamia tornator

Tetraopes humeralis

Tetraopes tetrophthalma

Tetraopes tetrophthalmus iowensis

Tetraopes tetropthalmus

Tetraopes tetropthalmus iowensis

Tetraopes tornator

Tetraopes tredecimpunctatus

Common Names

eastern milkweed longhorn beetle

red milkweed beetle

Glossary

Elytra

The hardened or leathery forewings of beetles used to protect the fragile hindwings, which are used for flying. Singular: elytron.

Femur

On insects and arachnids, the third, largest, most robust segment of the leg, coming immediately before the tibia. On humans, the thigh bone.

Pronotum

The exoskeletal plate on the upper side of the first segment of the thorax of an insect.

Scutellum

The exoskeletal plate covering the rearward (posterior) part of the middle segment of the thorax in some insects. In Coleoptera, Hemiptera, and Homoptera, the dorsal, often triangular plate behind the pronotum and between the bases of the front wings. In Diptera, the exoskeletal plate between the abdomen and the thorax.

Tarsus

The last two to five sections of an insect’s leg, attached to the tibia; the foot.

Visitor Photos

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Alfredo Colon

Red milkweed beetle, Tetraopes tetrophthalmus

Luciearl

red milkweed beetle 22 — Beetle on milkweed.

Cynthia Starkweather-Nelson

Red Milkweed Beetle crawling all over the Milkweed today.

Minnesota Seasons Photos

Slideshows

Red Milkweed Beetle
DianesDigitals

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Red Milkweed Beetle
Andree Reno Sanborn

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Visitor Sightings

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Alfredo Colon
7/1/2026

Location: Albany, NY

Rafael
7/2/2026

Location: Lansing, IL

Mariah
6/20/2026

Location: Saint Paul, MN

Luciearl
8/2/2025

Location: Lake Shore, MN

Cynthia Starkweather-Nelson
9/22/2023

Location: Burnett, MN

DW
6/15/2023

Location: Breezy Point, MN

Kathleen Monson
6/13/2023

Location: 5150 Woodridge Road, Minnetonka, MN 55345

I have a lot of milkweed in my vegetable garden. Should I move the plants?
Or how do I deal with this beetle?

John Valo
6/14/2023

Red milkweed adults eat the leaves of mostly common milkweed, and the larvae feed on the roots. They will not feed on other plants in your garden, and they do not harm monarch eggs or caterpillars.

If you have “a lot of” milkweed plants, consider letting them be. However, if you still want to get rid of the beetles, the best way is manually, knocking them into a bucket or pan of soapy water. Here is a link to a YouTube video showing how this works:

Quick, Easy, Inexpensive, and Effective Way To Get Rid of Milkweed Bugs

Luciearl
August 2022