Milkweed Tussock Moth: Good or Bad? Exploring Its Impact

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Milkweed plants are well-known for their association with monarch butterflies, as they serve as the sole host plant for monarch caterpillars. However, another insect that relies on milkweed for sustenance is the milkweed tussock moth caterpillar, which can often be found devouring the leaves of these plants. These hairy, brightly colored caterpillars raise the question: are milkweed tussock moths good or bad for our ecosystem?

The answer is not so simple, as the presence of milkweed tussock moth caterpillars can have both positive and negative effects on the environment. On one hand, these caterpillars are an essential part of the food chain, providing nourishment for various predators, such as birds and bats. Additionally, their feeding habits have been known to help control the spread of invasive milkweed species. On the other hand, the voracious appetite of these insects can potentially cause damage to milkweed plants, which may impact other species, like the monarch butterfly, that heavily rely on them for survival.

It is essential to consider both the pros and cons of the milkweed tussock moth caterpillars in order to take a balanced approach when discussing their role in our ecosystem.

Milkweed Tussock Moth Overview

Lifecycle and Appearance

The milkweed tussock moth, also known as Euchaetes egle, belongs to the family Erebidae and is a specialist herbivore that feeds on milkweed plants1. The caterpillar stage, known as the milkweed tussock caterpillar, is distinctively colorful with tufts of black, white, and orange hairs2. The adult moth is less colorful, featuring grayish-brown wings with a wingspan of about 1.5 inches3.

Eggs hatch in about 7-10 days, and the caterpillars feed on milkweed plants in clusters for 2-3 weeks before pupating4. The adult moths emerge after 10-20 days, and their lifespan is relatively short, lasting only a few weeks5.

Habitat and Range

Milkweed tussock moths are native to eastern North America and can be found from the Atlantic coast to the Rocky Mountains6. They prefer habitats with an abundance of milkweed plants, including fields, meadows, and roadsides7.

Features of the Milkweed Tussock Moth:

  • Specializes in feeding on milkweed plants
  • Colorful caterpillars with tufts of hair
  • Grayish-brown adult moths
  • Native to eastern North America

Characteristics of the Milkweed Tussock Moth:

  • Lifecycle from egg to adult takes 4-6 weeks
  • Caterpillars feed in clusters
  • Adults have a wingspan of about 1.5 inches

Effects on Garden and Ecosystem

Impact on Monarch Butterflies

Milkweed tussock moth caterpillars share a common food source with Monarch butterfly larvae: milkweed plants. These caterpillars can sometimes cause damage to milkweed plants as they have a strong appetite, but they usually have minimal impact on the Monarch butterfly population as they feed on different parts of the milkweed plant.

Benefits to Garden

Milkweed tussock moths benefit the garden and ecosystem by:

  • Supporting native species: These moths are native to North America and contribute to the natural balance of species in a garden.
  • Attracting pollinators: Milkweed plants are popular among several pollinators like bees and butterflies, fostering a biodiverse ecosystem.

Here’s a comparison table of milkweed tussock moths and Monarch butterflies in a garden:

Feature Milkweed Tussock Moth Monarch Butterfly
Habitat North America North America
Food Source Milkweed plants Milkweed plants
Impact on Milkweeds Moderate Minimal
Role in Ecosystem Native species Pollinators

By maintaining a diverse ecosystem and including native species like milkweed tussock moths, gardeners can support both plant and insect health in their gardens.

Management and Control

Preventing Infestations

To prevent milkweed tussock moth infestations, regularly check your milkweed plants. Look for the hairy caterpillars, especially in their early instars. Remove any caterpillars you find to prevent them from consuming the entire plant.

Another prevention tactic is planting different species of milkweed. Monarch butterflies prefer common milkweed, but they will also utilize swamp milkweed, butterflyweed, and whorled milkweed. These species tend to grow in clumps, making it harder for tussock moth caterpillars to infest them.

Natural Predators

There are several natural predators of the milkweed tussock moth. They help to keep their population in check. Some examples include:

  • Birds
  • Predatory insects

Encouraging natural predators in your garden can be an effective way to control tussock moth caterpillars. For instance, you can provide bird houses and plant flowers that attract beneficial insects.

Pros of Natural Predators Cons of Natural Predators
Help control tussock moth caterpillars Cannot always prevent entire infestations
Eco-friendly May also affect other insects or plants in your garden
No need for chemical control May require additional effort to attract and support natural predators

Relation to Other Species

Monarchs and Milkweed Tussock Moths

  • Monarchs lay eggs on milkweed plants, which provide a food source for their caterpillars.
  • Milkweed Tussock Moth caterpillars also feed on milkweed but share a different habitat.
  • Both caterpillars consume toxic compounds, making them unappetizing to predators.

Milkweed Aphids

  • Aphids are another species found feeding on milkweed plants.
  • They feed on plant sap, mainly avoiding the toxic sap found in the larger veins.

Here’s a comparison table of the characteristics of adult milkweed tussock moths, monarchs, and aphids:

Species Size Color/Pattern Habitat Diet
Adult Milkweed Tussock Moth Small-medium Gray color, with fuzzy appearance Mainly eastern North America Milkweed plants
Monarch Large Orange and black wing pattern North America, Mexico, Central America Milkweed plants
Aphid Very small Green or black (depending on species) Worldwide Plant sap (from milkweed)

These three species demonstrate unique relationships with milkweed plants:

  • Monarch butterflies rely on milkweed plants for their life cycle.
  • Milkweed Tussock Moths and aphids also depend on milkweed as a food source.

Although they share the same food source, these species do not seem to harm each other. They coexist on the milkweed plant and contribute to the overall ecological balance.

Footnotes

  1. https://hgic.clemson.edu/milkweed-tussock-moth-caterpillars/

  2. https://hgic.clemson.edu/milkweed-tussock-moth-caterpillars/

  3. https://hgic.clemson.edu/milkweed-tussock-moth-caterpillars/

  4. https://hgic.clemson.edu/milkweed-tussock-moth-caterpillars/

  5. https://hgic.clemson.edu/milkweed-tussock-moth-caterpillars/

  6. https://hort.extension.wisc.edu/articles/common-milkweed-insects/

  7. https://hort.extension.wisc.edu/articles/common-milkweed-insects/

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 – Milkweed Tussock Moth Caterpillars

 

spiny caterpillar
February 22, 2010
bugman,
found this caterpillar on milkweed last summer in northern illinois forest preserve. Can you please identify it
renu
Illinois, USA

Milkweed Tussock Moth Caterpillars

Dear renu,
These are Milkweed Tussock Moth Caterpillars, Euchaetes egle.  You may find more information on BugGuide.

Letter 2 – Milkweed Tussock Moth Caterpillar

 

Subject: What Type of Caterpillar Is This??
Location: Columbus, Ohio
August 20, 2016 6:57 am
Dear Mr. Bugman,
I’ve seen tons of caterpillars around my house recently but I’ve never seen any like this one. What type of caterpillar is this??
Signature: Samantha

Milkweed Tussock Moth Caterpillar
Milkweed Tussock Moth Caterpillar

Dear Samantha,
Do you have milkweed plants growing near your house?  We believe this is a Milkweed Tussock Moth Caterpillar,
Euchaetes egle, and it feeds on milkweed.  Though it seems lighter in color to individuals on our site, it does match this BugGuide image pretty closely.

That looks exactly like it, thank you!!

Letter 3 – Milkweed Tussock Moth Caterpillars

 

Subject: Milkweed diners
Location: SW Virginia
August 6, 2017 1:02 pm
Hi, what are these caterpillars I saw skeletonizing milkweed leaves? SW Virginia, late July. Thank you!
Signature: wondering

Milkweed Tussock Moth Caterpillars

Dear wondering,
These are Milkweed Tussock Moth Caterpillars, and they are a common species in eastern North America.

Letter 4 – Milkweed Tussock Moth Caterpillar

 

Subject:  Odd insect?
Geographic location of the bug:  Gouverneur NY
Date: 09/08/2017
Time: 07:52 PM EDT
So I was sitting outside waiting for my daughter to get holes from school. When she got off the bus, i was coming in the house with her and seen this odd looking insect. Snapped a picture because I found it rather interesting. No idea what it is.
How you want your letter signed:  S.Bush

Milkweed Tussock Moth Caterpillar

Dear S. Bush,
Your daughter must have been somewhere where milkweed was growing since your pictured Milkweed Tussock Moth Caterpillar is only found feeding on milkweed.

Letter 5 – Milkweed Tussock Moth Caterpillar

 

Subject:  Caterpillar
Geographic location of the bug:  Milkweed
Date: 08/09/2018
Time: 07:46 AM EDT
Your letter to the bugman:  Thi dc is not a monarch caterpillar
How you want your letter signed:  Sue

Milkweed Tussock Moth Caterpillar

Dear Sue,
Knowing the plant upon which an insect is found it is often extremely helpful for identification purposes, but not all insects are found on plants, so we don’t have a field for that purpose.  Milkweed is not a “Geographic location” and knowing if something was sighted in Pennsylvania or California or South Africa is also quite helpful, and every bug is found somewhere on the planet, which is why we have a Geographic location field on our submission form.  Having the Geographic location is also of assistance for persons scouring the internet for identification purposes, so we hope you will write back and provide an actual Geographic location so we don’t have to leave that field blank in our posting.  This is a Milkweed Tussock Moth Caterpillar, one of the many species, like the Monarch caterpillar, that depends upon milkweed for survival.  We don’t understand what “Thi dc” means since we could not locate it in the dictionary.

Letter 6 – Milkweed Tussock Moth Caterpillar

 

Subject:  Caterpillar
Geographic location of the bug:  Central PA
Date: 09/04/2021
Time: 01:29 PM EDT
Your letter to the bugman:  Is this poisonous? What type of caterpillar is this?
How you want your letter signed:  Jeff

Milkweed Tussock Moth Caterpillar

Dear Jeff,
This is a Milkweed Tussock Moth Caterpillar and it poses no threat to humans unlike other caterpillars that are known to sting.  Insects that feed on milkweed are able to incorporate toxins which make them distasteful or possibly even toxic to predators that eat them.

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: Tussock Moths

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3 Comments. Leave new

  • I found a fuzzy cat on my Milkweed, I live in Virginia, and this is my first time with the Monarch Butterfly blessing my garden

    Reply
  • These black & orange balls are eating all milkweed down to the stem. How can we get rid of them?

    Reply
    • We do not offer extermination advice. Milkweed is the host plant for many insects, not just Monarch caterpillars.

      Reply

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