Milkweed Beetle Life Cycle: A Fascinating Journey Unveiled

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Milkweed beetles are fascinating insects that have a unique relationship with milkweed plants. These red and black beetles belong to the genus Tetraopes and are part of the longhorned beetles family. They are known for their striking appearance and for feeding exclusively on milkweed, which allows them to accumulate toxins that provide protection from predators.

The life cycle of milkweed beetles is intriguing and includes four distinct stages: egg, larva, pupa, and adult. During this process, the beetles undergo complete metamorphosis, transforming from tiny eggs to voracious larvae that bore into milkweed roots, eventually becoming the colorful adults we recognize. Understanding the life cycle of these beetles can help gardeners and nature enthusiasts appreciate their role in the ecosystem and their importance in supporting healthy milkweed populations.

Some interesting features of milkweed beetles:

  • Bright red coloration serves as a warning to predators of their toxicity
  • Adults emerge in late spring to feed on milkweed plants
  • Larvae overwinter below ground, feeding on milkweed roots

Milkweed Beetle Life Cycle Stages

Eggs

Milkweed beetles lay their eggs on milkweed plants. The eggs are small and inconspicuous, typically laid in small groups. They hatch within a few days to a week.

Larvae

After hatching, milkweed beetle larvae begin feeding on milkweed roots. They have a grub-like appearance and spend most of their time below ground. Overwintering occurs in the larval stage, which lasts for several months.

Pupae

The larvae eventually transition into the pupal stage near milkweed plant roots. During this stage, the milkweed beetle undergoes a metamorphosis and prepares to become an adult.

Adult

Adult milkweed beetles emerge from their pupal stage in late spring. They are red with black spots or other markings, and their bright color serves as a warning to predators due to their toxic diet of milkweed plants. Adults feast on milkweed foliage and leaves, reproducing and completing the life cycle. One of the most common species is the red milkweed beetle (Tetraopes tetraophthalmus).

Mating and Reproduction

Mate Selection

Milkweed beetles, like other beetles, reproduce sexually. Males locate potential mates and perform courtship rituals to win the attention of the female. For example, a male beetle may stroke his antennae and front pair of legs on the female’s body to attract her interest.

Egg Laying

After mating, female beetles lay eggs on the milkweed plant, ensuring the next generation will have access to their preferred food source. The eggs hatch into larvae, which undergo several growth stages before becoming adult beetles capable of reproduction. The entire life cycle of a milkweed beetle is intricately connected to the milkweed plant, from egg-laying to feeding and eventual reproduction success.

Beetle Adaptations

Aposematism

Milkweed beetles, like many other insects, have developed a defense mechanism called aposematism. This involves having bright colors, such as the orange or reddish-orange shades often seen in Tetraopes spp. beetles, that warn predators of their toxic or unpalatable nature. The warning colors enable beetles to deter potential predators, allowing them to survive and reproduce.

Diet

Milkweed beetles, as their name suggests, primarily feed on milkweed plants. They specialize in consuming the leaves, seeds, and stems of various milkweed species. Due to this specialization, milkweed beetles can break down the toxic compounds found in milkweed plants and even use them as a defense mechanism. For example, Tetraopes tetraophthalmus, the red milkweed beetle, is most commonly found in Wisconsin and has a strong preference for milkweed as its food source.

Beetle Species Primary Diet
Tetraopes spp. Milkweed (various species)
  • Milkweed diet benefits
    • Ability to tolerate and break down toxic compounds
    • Fewer competitors for food resources
    • Utilization of toxins for defense against predators
  • Milkweed diet drawbacks
    • Limited food options
    • Dependency on milkweed availability
    • Potential vulnerability to changes in milkweed populations

Ecological Importance

Pollination

Milkweed plants play a crucial role in the pollination process, as they are the primary food source for monarch butterfly caterpillars1. Monarchs lay their eggs on milkweed leaves, providing a necessary element in their reproductive cycle. Besides monarchs, milkweed flowers attract various pollinators, including bees and other butterflies, thereby supporting the local ecosystem2.

Pest Control

Milkweed beetles, like the red milkweed beetle (Tetraopes tetraophthalmus), are considered beneficial insects as they primarily feed on milkweed plants3. While they can defoliate milkweed plants to some extent, they do not cause significant damage, and their consumption can help control the growth of milkweed, preventing it from becoming invasive4. As a result, these beetles contribute to a balanced ecosystem with natural pest control.


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Conservation Issues

Milkweed Decline

Milkweed plants are crucial for the survival of monarch butterflies, as they are the sole host plant for their caterpillars. However, milkweed has been declining due to factors such as habitat loss, pesticide use, and roadside management practices. This decline affects not only monarch butterflies but also other species that rely on milkweed, such as the large and small milkweed bugs1.

  • Habitat loss: Urbanization, agriculture, and other land alterations have led to the loss of milkweed habitat.
  • Pesticide use: Insecticides and herbicides can harm milkweed plants, as well as the insects that depend on them.
  • Roadside management: Mowing and the use of herbicides along roadsides can reduce milkweed availability.

Habitat Fragmentation

Habitat fragmentation is another issue impacting milkweed and the species that depend on it. As habitats become increasingly isolated due to human activities, it becomes more difficult for species such as the milkweed beetle and monarch butterflies to disperse and maintain healthy populations2.

  • Limited connectivity: Fragmented habitats make it harder for plants and animals to move between areas, increasing their vulnerability.
  • Genetic isolation: Isolated populations can suffer from reduced genetic diversity, affecting their ability to adapt to environmental changes.
Factor Milkweed Decline Habitat Fragmentation
Habitat Loss Yes Yes
Pesticide Usage Yes No
Roadside Management Yes No
Limited Connectivity No Yes
Genetic Isolation No Yes

Footnotes

  1. Milkweed and Monarchs 2
  2. More than monarchs – What are those bugs on my milkweed? 2
  3. Common Milkweed Insects – Wisconsin Horticulture
  4. Spreading milkweed, not myths | U.S. Fish & Wildlife Service

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

 

Moth, beetle, & spawn in southern Ontario
Tue, Jun 16, 2009 at 4:44 PM
I have three bugs I’d like identified. All photos were taken today in my backyard (date is on the photos). I live in Hamilton, Ontario (Canada).
… 2)Beetle.jpg – I found this one on my patio, it also chose not to fly, so I took photos of it then released it. Has orange and black stripes. … Help in identifying these 3 bugs would be greatly appreciated.
Thank you, Luke.
Hamilton, Ontario, Canada

Swamp Milkweed Beetle
Swamp Milkweed Beetle

Hi Luke,
Posting letters with multiple photos of unrelated species is something we frown upon because of all the extra labor involved and also because of the problems with our archiving and categorization process. Your beetle appears to be a Swamp Milkweed Beetle, Labidomera clivicollis, one of the Leaf Beetles. This is a beetle with much variation in the markings, but one photo on BugGuide looks nearly identical to your specimen. According to BugGuide: “Part of the orange and black milkweed mimicry complex, which inlcudes Monarch butterfly, Red Milkweed Beetle, Milkweed bugs, and at least one assassin bug. Both 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. ”
P.S. Your other requests are a Virginia Ctenuchid Moth and Spittlebug.

Update: from Eric Eaton
Daniel:
The swamp milkweed beetle ID is right on.  I don’t have the time at the moment to research the plant bug beyond family level, and that is also correct (Miridae).
Eric

Letter 2 – Swamp Milkweed Beetle

 

Colorful Beetle
I found this colorful beetle, which at first glance appears to be a super laybird beetle, on swamp milkweed in a garden in Milwaukee, WI on July 19, 2008. Two views.
Bob

Hi Bob,
You actually had your answer in your question. You knew it was a beetle and you knew it was on swamp milkweed, and it is a Swamp Milkweed Beetle, Labidomera clivicollis.

Letter 3 – Swamp Milkweed Beetle

 

mystery beetle in Nashville, TN
September 5, 2009
Hi, I saw this beetle last week. Could it be a type of lady beetle or Harlequin beetle? Something else? Seemed larger than a typical ladybug. Did not get a chance to really measure though. It moved quickly. Any info appreciated. (Enjoying your site!)
Carrie Nunes
Nashville, TN

Swamp Milkweed Beetle
Swamp Milkweed Beetle

Hi Carrie,
Your beetle is a Leaf Beetle known as a Swamp Milkweed Beetle.  It is not related to the Ladybird Beetles.

Letter 4 – Swamp Milkweed Beetle

 

small beautiful bug
May 29, 2009
Subject was located on pigeonberry plant near a garden. About 1/2″ long. Only one specimen found.
Betsy
Central Texas

Swamp Milkweed Beetle
Swamp Milkweed Beetle

Hi Betsy,
Your letter originally arrived at a very busy mail period for us, and it coincided with the end of the semester and a hasty retreat to visit Mom in Ohio.  Needless to say, there was so much mail when we returned to the office, much of it remained unanswered.  This is a Swamp Milkweed Beetle, Labidomera clivicollis.  You can read more about it on BugGuide which states: “Occur in every state east of the Rocky Mountains, and into northern Mexico.

Authors

  • 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.

    View all posts
  • 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.

    View all posts
Tags: Milkweed Beetle

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1 Comment. Leave new

  • Kris Wallner
    July 7, 2009 10:43 am

    Is the Red Milweed Beetle a beneficial bug or should I squish it and try to erradicate from my garden?

    Reply

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