Milkweed Beetle: All You Need to Know in a Nutshell

Milkweed beetles are fascinating creatures that have uniquely adapted to life on milkweed plants. These little insects, belonging to the longhorn beetle family, use the milkweed as their primary source of food and habitat. With their stunning red and black appearances, they have carved out a niche for themselves in nature, mainly due to their ability to consume toxic milkweed plants without being harmed.

Their vibrant coloration serves a purpose beyond aesthetics, acting as a warning signal to predators that they are toxic and not to be messed with. As they munch on milkweed leaves, stems, and roots, they acquire toxins from the plant, which makes them unpalatable to most predators. This survival mechanism, combined with their fascinating life cycle, make the milkweed beetle a captivating subject for study and observation.

Various species of milkweed beetles exist across North America, each preferring a specific type of milkweed. For example, the red milkweed beetle (Tetraopes tetraophthalmus) is commonly found in Wisconsin and other parts of the eastern United States, while other species thrive in various regions throughout the Americas. So, whether you’re a casual observer or an avid gardener, getting to know more about these amazing beetles is a rewarding experience.

Milkweed Beetle Basics

Appearance and Identification

The milkweed beetles, particularly the red milkweed beetle (Tetraopes tetrophthalmus), are known for their distinctive appearance. They have:

  • Bright red or orange bodies
  • Black marks on their elytra (wing covers)
  • Four eyes, with each compound eye divided by the antennae

The blue milkweed beetle is another example, displaying a bright blue color with black markings.

Scientific Name and Classification

Milkweed beetles belong to the longhorn beetle family, Cerambycidae, and the genus Tetraopes. Some key features of this classification include:

  • Long antennae, often as long as their body
  • Elytra that cover the abdomen
  • A plant-based diet, primarily feeding on milkweed species
Feature Red Milkweed Beetle Blue Milkweed Beetle
Scientific name Tetraopes tetrophthalmus Tetraopes sp.
Family Cerambycidae Cerambycidae
Body color Bright red or orange Bright blue
Markings on elytra Black Black
Eyes Four (divided by antennae) Four (divided by antennae)
Primary food source Milkweed species Milkweed species

By understanding the appearance and classification of milkweed beetles, you can easier identify and appreciate these fascinating insects.

Life Cycle and Reproduction

Eggs

Female Milkweed Beetles lay their eggs on milkweed plants. The eggs are small and oval-shaped, usually found on the underside of milkweed leaves. A mother beetle will typically lay between 30 and 40 eggs in her lifetime.

  • Eggs are laid on milkweed plants
  • Oval-shaped and found on the underside of leaves
  • Typically 30-40 eggs per female

Larvae and Nymphs

After the eggs hatch, the beetle goes through a larval stage. During this stage, they are called “nymphs” and go through several growth stages called “instars”. The nymphs undergo several molts, shedding their outer skin as they grow, and develop through 4 different instars. The nymphs feed on milkweed leaves and gather nutrients to grow and develop into adults.

  • Nymphs have several growth stages called instars
  • Undergo molts during instars
  • Feed on milkweed leaves for nourishment

Adult Stage

Once the nymphs complete their growth and development, they enter the adult stage. Adult Milkweed Beetles are typically vibrant in color, with patterns that make them easily recognizable. At this stage, they are capable of reproduction, allowing the life cycle to continue.

  • Vibrant colors and recognizable patterns
  • Capable of reproduction
Life Stage Key Features
Eggs Laid on milkweed, 30-40 per female
Larvae & Nymphs Multiple instars, feed on milkweed
Adult Vibrant colors, capable of reproduction

Habitat and Distribution

Host Plants

The Milkweed Beetle primarily feeds on milkweed plants within the genus Asclepias. Some common species of milkweed plants include:

  • Asclepias syriaca (common milkweed)
  • Asclepias incarnata (swamp milkweed)

These plants serve as both a source of food and a breeding ground for beetles.

Regional Distribution

Milkweed Beetles are native to North America and Central America, with some specific distribution details including:

  • Red Milkweed Beetles (Tetraopes spp.) can be found in the eastern United States1
  • Large and small Milkweed Bugs (Oncopeltus fasciatus) are more widespread, found throughout the continent2

It is important to note that different species of Milkweed Beetles might be found in various regions, and they often prefer specific species of milkweed plants.

Comparing Common Milkweed and Swamp Milkweed

Feature Common Milkweed (Asclepias syriaca) Swamp Milkweed (Asclepias incarnata)
Flower Color Purple-pink to white3 Light pink to mauve4
Habitat Fields, roadsides, and waste areas3 Swamps, wet meadows, and riverbanks4
Soil Preference Well-drained3 Moist to wet4

Interactions with Milkweed

Feeding Habits

The Milkweed Beetle, specifically the Red Milkweed Beetle (Tetraopes tetraophthalmus), is known to feed on various species of milkweed plants. They preferentially lay their eggs on milkweed plants where the larvae can feed on the roots. As adults, they primarily consume the plant’s leaves, flowers, and seed pods.

Milkweed plant parts consumed:

  • Leaves
  • Flowers
  • Seed pods

Toxicity and Protection

Milkweed plants contain a toxic latex in their sap, which contains toxic compounds called cardiac glycosides. These compounds are harmful to many animals, including humans, if ingested. Milkweed Beetles have evolved to not only tolerate these toxins but also use them as protection against predators.

When consuming milkweed, the beetles store the toxic compounds in their bodies, making them unappetizing and dangerous to potential predators. Their bright red and black coloration further warns predators of their toxicity.

Toxic compounds in milkweed:

  • Latex sap
  • Cardiac glycosides

Beetle protection mechanisms:

  • Store toxins in their bodies
  • Warning coloration (red and black)

Comparison of milkweed vs. non-milkweed feeders:

Property Milkweed Feeders (e.g., Milkweed Beetle) Non-Milkweed Feeders (Other insects)
Toxicity Tolerates and stores milkweed toxins May be harmed by milkweed toxins
Defense Uses toxins as protection against predators No adaptation to milkweed toxins
Coloration Bright colors (warning) Varies

Ecological Role and Impact

Milkweed Specialists

Milkweed beetles (Tetraopes spp.) are part of a larger group of insects that specialize in feeding on milkweed plants. Some common examples include:

  • Red milkweed beetles (Tetraopes tetrophthalmus)
  • Swamp milkweed leaf beetles (Labidomera clivicollis)

These beetles have adapted to feed on milkweed plants despite their toxic properties, and they play a crucial role in milkweed ecosystems.

Monarch Butterflies and Caterpillars

Milkweed plants are essential for monarch butterflies and their caterpillars, as they are the sole host plants for these insects. Monarchs lay their eggs on milkweed plants, and the caterpillars feed on the leaves, making milkweed vital for their survival and reproduction.

Milkweed Bugs and Other Insects

In addition to milkweed beetles and monarchs, milkweed plants also host a variety of other insects. Some of these insects include:

  • Milkweed bugs (Oncopeltus fasciatus)
  • Aphids (Aphis nerii)
  • Milkweed tiger moths (Euchaetes egle)

These insects feed on various parts of the milkweed plant, such as seeds, leaves, and nectar, and they play essential roles in the milkweed ecosystem.

Predators and Prey

Many milkweed-associated insects, including milkweed beetles, serve as prey for predators like birds, spiders, and other insects. Simultaneously, these insects help control milkweed populations, ensuring a balance within the ecosystem.

Here’s a comparison table of milkweed specialists:

Insect Adaptation to Milkweed Role in Ecosystem
Milkweed Beetle Feeds on leaves Controls milkweed growth
Monarch Butterfly Lays eggs on milkweed Pollinator
Swamp Milkweed Beetle Feeds on leaves Controls milkweed growth
Milkweed Bug Feeds on seeds Seed dispersal, pollinator
Aphid Feeds on plant sap Provides food for predators
Milkweed Tiger Moth Feeds on leaves as a larva Predator control

In conclusion, the ecological role and impact of milkweed beetles and other milkweed-dependent insects are vast and interconnected, contributing to the overall health and diversity of ecosystems where milkweed plants grow.

In Gardens and Landscapes

Attracting and Supporting Milkweed Beetles

Milkweed beetles, such as the red milkweed beetle (Tetraopes tetraophthalmus), are milkweed specialists, with 26 different species in the Tetraopes genus, each preferring a specific species of milkweed1. To support milkweed beetles, gardeners can plant a variety of native milkweed species such as common milkweed (Asclepias syriaca), swamp milkweed (Asclepias incarnata), and butterflyweed (Asclepias tuberosa)2.

Milkweed plants provide nectar and serve as a food source for beetle larvae. Milkweed also contains toxins, which the beetles can internalize to deter predators3. However, note the potential toxicity of milkweed when planting around children or pets.

Dealing with Pests and Invasive Species

While milkweed is a native plant with many beneficial insects, some gardeners may face challenges with pests and potential invasive issues4.

Pros of Milkweed in Gardens:

  • Supports milkweed beetles, monarch butterflies, and other pollinators
  • Provides nectar and food for many insects and animals

Cons of Milkweed in Gardens:

  • Can spread quickly in certain environments
  • May attract unwanted insects, such as milkweed bugs5
  • Potential toxicity to children or pets

Here are some tips for dealing with pests and invasive species:

  • Wear gloves while handling milkweed, as it can be poisonous to humans and animals3.
  • Monitor your milkweed population and pull out or trim plants that encroach on other desired plants.
  • Utilize non-chemical methods to manage pests, such as utilizing a garden hose to dislodge unwanted insects or encouraging natural predators like birds.
  • Maintain leaf litter and other habitat features that support the complete metamorphosis of milkweed beetles.

In conclusion, milkweed is an important plant for supporting the population of milkweed beetles. By planting a variety of milkweed species and following these tips, gardeners can create a healthy environment for beetles and other pollinators while managing potential challenges related to pests and invasive species.

Interesting Facts and Trivia

  • Large milkweed bugs (Oncopeltus fasciatus) and small milkweed bugs (Lygaeus kalmii) are both commonly found on milkweed plants.
  • They belong to the true bug order, Hemiptera, and have an incomplete metamorphosis.

Milkweed plants, like common milkweed and swamp milkweed, are vital host plants for various insects, including:

  • Monarch butterfly caterpillars
  • Milkweed tussock moth caterpillars
  • Oleander aphids

A few fascinating features of milkweed bugs are:

  • They have a long, straw-like mouthpart called a proboscis for feeding.
  • They exhibit warning colors to deter predators due to the toxins they acquire from milkweed plants.
Milkweed Bugs Large Milkweed Bug (Oncopeltus fasciatus) Small Milkweed Bug (Lygaeus kalmii)
Size ¾” long Smaller
Color Pattern Orange to reddish-orange with black band Red and black
Preferred Habitat Common milkweed Various milkweed species
  • Milkweed bugs can overwinter, surviving in a gray cocoon for extended periods.

Aphids on milkweed plants, such as oleander aphids, secrete a sticky substance called honeydew, which can lead to sooty mold on the leaves. Monarch butterfly caterpillars and other insects are not affected by this mold.

Identifying milkweed bugs can be done through their distinct color patterns and by observing them on milkweed plants, specifically around seed pods.

That’s a brief look at some interesting facts and trivia about milkweed beetles and the plants they call home.

Footnotes

  1. Wisconsin Horticulture 2

  2. NC State Extension Publications 2

  3. US Forest Service 2 3 4 5

  4. Missouri Botanical Garden 2 3 4

  5. Good Growing – More than monarchs – What are those bugs on my milkweed?

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Swamp Milkweed Beetle

 

Mystery Ladybug?
November 5, 2009
Hi. I found this insect hanging out on the leaf of a tall Conyza canadensis growing in my back yard in Denton, Texas at the end of October. It looks to me like a member of Coccinellidae, but I can’t find it on any lists.
GTony
Denton, Texas, USA

Swamp Milkweed Beetle
Swamp Milkweed Beetle

Hi GTony,
We were a bit busy when your letter originally arrived, and we are posting it two months late.  Though it appears to be a Lady Beetle, this is not a Ladybug, but rather, a Swamp Milkweed Beetle, Labidomera clivicollis.  You may verify this on BugGuide.

Letter 2 – Swamp Milkweed Beetle

 

round red and black beetle
Location: Northeast Illinois
May 29, 2011 9:32 pm
Hello. I saw this beetle on my butterfly weed at dusk. It was very shiny, round, highly domed, and larger than a normal ladybug – maybe half an inch across.
Can you ID it? Thanks!
Signature: Clare

Swamp Milkweed Beetle

Hi Clare,
WE are guessing that the plant you are calling “butterfly weed” is actually a species of Milkweed because this is a Swamp Milkweed Beetle,
Labidomera clivicollis.  The caterpillars of the Monarch Butterfly feed on Milkweed and the flowers attract numerous species of butterflies.  Many of the insects that feed on milkweed have aposomatic warning coloration (black and red) as feeding on milkweed either makes them distasteful or possibly toxic to predators.

Letter 3 – Swamp Milkweed Beetle

 

What kind of beetle is this?
Location: Marion county, Missouri. USA
June 5, 2011 4:56 pm
This bug was found in Marion county, Missouri. We are not sure what kind of beetle it is.
Signature: Brian

Swamp Milkweed Beetle

Hi Brian,
The beetle in question is a Swamp Milkweed Beetle,
Labidomera clivicollis, and there is considerable variation between individuals in both the coloration and the extent of the black markings.

Letter 4 – Swamp Milkweed Beetle

 

Subject: I know its not a ladybug, but what is it?
Location: Norman, OK
March 6, 2014 3:27 pm
hopefully you can figure this out, I’ve had troubles identifying it. thank you! it is much larger than a ladybug and doesn’t have the same type of head and the antennae don’t seem remotely familiar… spots AND stripes? or would they be more like squares? lol
Signature: Lox

Swamp Milkweed Beetle
Swamp Milkweed Beetle

Dear Lox,
This sure looks like a Swamp Milkweed Beetle,
Labidomera clivicollis.  The black spotting pattern of the Swamp Milkweed Beetle is highly variable, and some individuals have more black than others.  BugGuide notes:  “Part of the orange and black milkweed mimicry complex, which includes Monarch Butterfly, Red Milkweed Beetle, milkweed bugs, and at least one assassin bug.   Larvae and adults of this species cut several side-veins of a milkweed leaf prior to feeding, to reduce the sticky latex that would otherwise be produced at their feeding sites. “

Yay! thank you so much!! I do believe you are correct, I would’ve never figured it out, as I’m not exactly knowledgeable about insects. It does make sense tho, because there where it was heading was a bunch of milkweed all around some rosebushes! now I feel better lol!

Authors

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  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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