Unicorn Caterpillar: All You Need To Know

This article is a guide on everything that you need to know about the Unicorn Caterpillar.

The unicorn caterpillar is a special ​​species of caterpillar that possess a unique horn-like protrusion that helps it spray its predators with acid.

Smartly camouflaging themselves against half-eaten leaves, these caterpillars are capable of infesting plants and killing them with their voracious feeding spread over the summer months.

Let’s look at these caterpillars and the moths they develop into.

What Are Unicorn Caterpillars?

Coelodasys unicornis, or the unicorn caterpillar, is the larval version of the brown and variegated unicorn caterpillar moth.

They are commonly found in the North American continent and belong to the family of Notodontidae or “prominent moths.”

Earlier, the caterpillar was placed under the genus of Schizura but was shifted to the Coelodasys genus based on papers published in 2021.

What Do Unicorn Caterpillars Look Like?

As larvae, they have a segmented body, with the second and third segments being green. The rest of their body is uniformly brown.

Their name comes from the horn-like protrusion that the larvae have at the head of their first segment.

The eighth segment has another smaller protrusion. Larvae are less than 1.49 inches in length.

The hump can spray a jet of defense liquid consisting of formic acid, which can cause skin irritation and burning.

As adults, they transform into a moth with a mottled or variegated bodies.

The forewing colors may range from maroon to purple, with spots that are rose, yellow, or brown in color.

The hindwings are shades of grey, with females having darker hindwings than males.

The base of their body has a greenish-white color followed by two dark lines. When at rest, adults fold their wings into a tent-like shape.

Unicorn Caterpillar
Image via Flickr by dominik18s

What Does A Unicorn Caterpillar Eat?

The unicorn caterpillar larvae are voracious eaters. They feed on leaves and leave large, gaping holes, which can eventually weaken and kill the plant.

Larvae feed on deciduous trees like aspen, oak, birch, and other broadleaf plants.

They have to chew mouthparts that help them eat through the leaves.

Their feeding time extends from spring all the way to fall while they overwinter in cocoons.

Adults, on the other hand, have a siphon-like mouth part that allows them to extract nectar.

Adult moths are not harmful to plants and actually help with pollination.

Where Do Unicorn Caterpillars Live?

Their population is distributed throughout North America. they were first discovered by James Edward Smith.

They are found in all the states of the United States and parts of Canada.

They are found in leaf litter and on host plants.

Eggs are laid on the tip or leaf edge of cherry leaves. Both larvae and adults are great camouflagers.

Any deciduous woodlands or shrubbery can contain eggs and larvae.

Life Cycle of A Unicorn Caterpillar

Unicorn caterpillar moths lay leaves on the tip of cherry leaves.

These hatch into caterpillar instars at around May in the South and June in the North.

The caterpillars are shaped to resemble brown dried leaves and have exceptional camouflage against cherry leaves.

They feed on the leaves and go into a white and flimsy cocoon in the fall, usually under leaf litter.

Adult moths emerge from this after the winter. They have approximately one generation per year.

How Long Do Unicorn Caterpillars Live?

Caterpillars can live for many months, with the average larvae feeding on leaves for a period of four months between spring and fall.

Some caterpillar species feed for years, overwintering in multiple pupal stages – however, the unicorn caterpillar undergoes only one.

As adults, their lifespan is comparatively short, with the sole purpose being to find a mate.

While we don’t know exactly how long the unicorn moth survives, most moths have a short lifespan ranging from a few days to a few weeks.

Unicorn Caterpillar
Adult Unicorn Moth. Image via Flickr by Anita Gould

Do They Bite?

A unicorn caterpillar cannot bite, and neither can an adult unicorn moth.

Both do not have biting mouth parts and are more likely to use other defense mechanisms than bite.

However, it’s best not to disturb unicorn caterpillars as they can spray a nasty jet of acid onto your skin.

Are They Poisonous/Venomous?

A unicorn caterpillar can shoot a spray of formic acid from the hornlike protuberance on its body.

This can cause painful blisters on coming in contact with human skin.

While it is not poisonous per se, it is corrosive and causes the skin to burn and sting. It’s best to seek medical advice if you get sprayed on.

Adults do not possess this capability and are hence neither poisonous nor venomous. However, some people are allergic to the powdery residue on moth wings.

Are They Harmful or Beneficial to Humans?

As larvae, the caterpillars can infest gardens and leave large holes in leaves. A group can destroy all leaves in a plant, causing it to die.

However, it’s best to use organic ways such as neem oil rather than insecticides to get rid of them.

Moths are beneficial as they help in pollinating plants.

What Are Unicorn Caterpillars Attracted To?

As adults, the moths are attracted to light. Due to this, they might often end up inside homes.

Larvae, on the other hand, are mostly nocturnal and attracted to host plants that include broadleaf plants and shrubs.

They retire to darker spaces and crevices, such as tree hollows, under rocks, and leaf litter.

How To Get Rid of Unicorn Caterpillars?

Some common methods of getting rid of unicorn caterpillars are:

If they are few in number, you can simply pluck them off and kill them in soapy water or place them elsewhere.

Remember to do this while wearing appropriate gear on your face and hands to protect yourself from their defense spray.

Try to create a bird bath or feeding zone. This will attract their natural predators and cause a decrease in numbers.

Alternatively, you can try to catch them by laying down a burlap at the base of the tree or on leaf litter.

As the caterpillars go into hiding, they might use the burlap, which you can then get rid of.

Make an organic insecticidal soap spray, or spray your plants with neem oil.

Finally, you can use commercial pesticides. However, these will also harm your plants and other beneficial insects.

Alternatively, you can look for degreed professionals who can help you with infestations.

Interesting Facts About Unicorn Caterpillars

Unicorn caterpillars are geta at camouflaging and are very well-suited to their surroundings.

The green segments, brown markings and dots, and overall shape of the body resemble a fried leaf that is curling at the edges.

It is theorized that the glands in the caterpillar’s body that help them spray formic acid take up almost 1/10th of the space within their body volume.

Adult moths are only 0.7 inches to 0.9 inches in size.

Sometimes, parasitoid wasps will prey on unicorn caterpillars.

The parasite will turn the caterpillar into a zombie version of itself that will then guard the wasp eggs and finally turn into food for the larvae.

Frequently Asked Questions

What does a unicorn caterpillar turn into?

Unicorn caterpillars turn into unicorn caterpillar moths.
There are two varieties of these moths: unicorn prominent or variegated prominent.
These names come from the bodies of the adults: the prominent ones are mottled, whereas the variegated are true to their name.

What do unicorn caterpillars eat?

Unicorn caterpillars mainly eat leaves from willow and cottonwood trees.
These caterpillars feed on the leaves of the tree throughout their larval stage, slowly munching away until it is ready for their transformation.
As adults, unicorn caterpillars feed off of nectar from flowers found nearby to its host tree.
It is important to note that adults rarely return to feed on the willow or cottonwood trees after their metamorphosis.

Why do caterpillars form a circle?

Caterpillars form a circle when they need to rest or sleep.
By forming a circle, they are able to protect themselves from potential predators.
As an additional protection measure, the caterpillars link their tails together to form a tight knot that is difficult for predators to penetrate.
Furthermore, the caterpillars’ circle formation helps them stay warm during the night by creating a buffer around them of their own body heat.

What animal kills caterpillars?

The primary predators of caterpillars are birds, who often choose to eat them as part of their regular diet.
Other insectivorous animals, such as many mammals, amphibians, reptiles, and spiders, also consume caterpillars.
Especially wasps and ants that are attracted by the pheromones produced by the caterpillar’s body can kill a large number of them in a short amount of time.
In addition, parasitic fungi infect dormant caterpillars and eventually kill them when they awake from dormancy.

Wrap Up

Little research has been done on these caterpillars, and much is unknown about their habits and growth.

However, we do know that while they’re highly beneficial as moths, it’s best to remove unicorn caterpillars from a garden, as they pose a risk to children and pests.

Caterpillars are an essential part of the pollinating ecosystem, and hence, try to transfer them instead of disposing of them.

You can also keep them in a closed indoor terrarium to observe their growth.

Thank you for reading.

Reader Emails

Unicorn caterpillars are attractive creatures that have often caused our readers to inquire with us as to what they are.

Please go through some of these letters to understand the queries, and also go through some of the pics of these beautiful caterpillars.

Letter 1 – Another Unicorn or False Unicorn Caterpillar

 

Caterpillar found in blueberry bushes September 23, 2009 I found this caterpillar taking a ride on my son’s shirt during an early morning of blueberry picking. I took its picture on my finger to show the size, and then we happily set it back onto a blueberry bush. I can’t find an identification for it. Thank you! Nichole Michigan (Ann Arbor area) in the summer (end of August)
Unicorn Caterpillar, or imposter???
Unicorn Caterpillar, or imposter???
Hi Nichole, Interestingly, we just finished posting another photo of a Unicorn Caterpillar, or False Unicorn Caterpillar from the genus Schizura.  Your photo with the translucent talon, we mean fingernail, is awesome.
Unicorn Caterpillar? or False Unicorn Caterpillar??
Unicorn Caterpillar? or False Unicorn Caterpillar??

Letter 2 – Unicorn Caterpillar

 

Early Instar Unicorn Caterpillar Location: S. Illinois August 22, 2011 6:01 pm Think this is an early instar unicorn caterpillar. Right about an inch long, on oak. This image is a little sharper than the one I sent along last year. Signature: Bert
Unicorn Caterpillar
Dear Bert, This does appear to be a Unicorn Caterpillar or another closely related member of the same genus Schizura based on photos posted to BugGuide.  If it is significantly smaller than the image you sent last year, it is most likely an earlier instar, though we cannot tell scale by comparing the two images.

Letter 3 – Unicorn Caterpillar? or False Unicorn Caterpillar, perhaps??

 

Unicorn Caterpillar September 23, 2009 Was walking with the 2 year old in the swamp park in Southern Illinois today and found a strange looking caterpillar. Some research has it as a Schizura unicornis (I think…do they eat oak?). The camouflage was strikingly good from some angles, the green “window” in its mid-section is exactly as translucent as leaves with the sun behind them. Thought you might like some pictures. Bert in Illinois Southern Illinois
Possibly Unicorn Caterpillar
Possibly Unicorn Caterpillar
Dear Bert, BugGuide lists the food plants of the Unicorn Caterpillar as:  “alder, apple, Trembling Aspen (Populus tremuloides), White Birch (Betula papyrifera), elm, hawthorn, hickory, willow“, while the closely related and similar looking Morning Glory Prominent or False Unicorn Caterpillar has its food plants listed as:  “leaves of beech, birch, elm, maple, morning-glory, oak, rose, and other woody plants” on BugGuide.  We would entertain the possibility that the list of plants for the Unicorn Caterpillar might be incomplete, and that your caterpillar might be either species.

Letter 4 – Unicorn Caterpillars

 

Found on a rose leaf I found several of these caterpillars on my rose bush and I can not find any info on it. can you help? Ann Hi Ann, These are a type of Prominent Moth Caterpillar known as the Unicorn Caterpillar, Schizura unicornis. BugGuide lists many food plants, including apple (related to rose), willow, alder, hickory, aspen, birch and elm.

Authors

    by
  • 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.

8 thoughts on “Unicorn Caterpillar: All You Need To Know”

    • Caterpillars generally do not do lasting harm to trees unless the caterpillars are so numerous as to defoliate an already weakened tree. We do not provide extermination advice.

      Reply

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