Imperial moth caterpillars are large, visually stunning insects that can catch the attention of nature enthusiasts and curious observers alike.
These caterpillars exhibit a wide range of color variations, from light to dark green or orange to dark brown, and even nearly black.
They can grow up to 5.5 inches in size, making them an interesting sight to behold.
Are Imperial Moth Caterpillars Poisonous?
An important question arises when discussing these creatures: are they poisonous?
While some may deliver toxins through their spines or setae, it is worth noting that these caterpillars do not fall into this category.
They do not pose any significant threat or health hazard to humans, as they are not venomous or poisonous, allowing people to appreciate their beauty without worry.
Imperial Moth Caterpillar Overview
The Imperial Moth Caterpillar (Eacles imperialis) is a large, showy insect that falls under the family Saturniidae within the order Lepidoptera.
Known for its striking appearance and size, it is a fascinating creature to observe.
These caterpillars can grow up to 5.5 inches in length.
They are highly variable in appearance, ranging from light to dark green or brown, often with spiny horns on their front thoracic segments.
Since they primarily feed on the foliage of host plants, gardeners and nature enthusiasts may occasionally encounter them.
Despite their intimidating appearance, Imperial Moth Caterpillars are not poisonous.
They don’t pose any threat to humans, making them an interesting subject for study and admiration.
When comparing the Imperial Moth Caterpillar to other caterpillars within the Lepidoptera order, their most notable characteristic is their impressive size and intricate color patterns.
The table below offers a brief comparison:
| Feature | Imperial Moth Caterpillar | Other Lepidoptera Caterpillars |
|---|---|---|
| Size | Up to 5.5 inches | Varies, often smaller |
| Color | Green or brown | Varies widely |
| Horns | Spiny and prominent | May or may not have horns |
Physical Characteristics and Variations
Coloration and Patterns
Imperial moth caterpillars exhibit a diverse range of colors, including yellow, purple, and yellow-green. Their bodies may have:
- White spots
- Orange spots
- Eyespots
These patterns help them blend in with their surroundings and deter predators.
Spines, Tubercles, and Stinging Hairs
Imperial moth caterpillars possess spines and tubercles but lack stinging hairs. This means that they:
- Are not poisonous
- Do not cause skin irritation when handled
Size and Sexual Dimorphism
Imperial moth caterpillars can grow up to 5.5 inches in length. There is little sexual dimorphism, meaning that:
- Males and females are similar in size
- Both sexes have similar coloration and patterns
Here’s a comparison table summarizing the features of Imperial moth caterpillars:
| Features | Imperial Moth Caterpillars |
|---|---|
| Colors | Yellow, Purple, Yellow-Green |
| Patterns | White spots, Orange spots, Eyespots |
| Spines and Tubercles | Yes |
| Stinging Hairs | No |
| Size | Up to 5.5 inches |
| Sexual Dimorphism | Minimal |
Remember to handle the Imperial moth caterpillars gently, as they are not poisonous and do not cause irritation.
Life Cycle and Development
Eggs and Larvae
Imperial moth caterpillars begin their lives as eggs laid on the foliage of host plants. These eggs are flattened spheres around 1/8 inch across. Once hatched, the larvae grow and develop through multiple stages, known as instars.
Some characteristics of the larvae include:
- Large size: up to 5.5 inches
- Variable appearance
- Spiracles for respiration
Pupa and Adult Moth
The pupa stage, also referred to as chrysalis, is when the caterpillar undergoes metamorphosis. Some features of the pupa include:
- Formation within a cocoon
- No feeding during development
When the metamorphosis completes, an adult moth emerges with fully developed wings. The adult moth exhibits traits such as:
- Wingspan: varies, but large
- Flying: primarily at night
- Mating to produce offspring
Here’s a comparison table of the different stages:
| Stage | Size | Appearance | Main Activity |
|---|---|---|---|
| Eggs | Small (laid as individual eggs) | Found on foliage | Hatching into larvae |
| Larvae | Up to 5.5 inches | Variable, spiracles visible | Feeding and growing |
| Pupa | Variable, but usually larger | Chrysalis formation | Metamorphosing |
| Adult Moth | Large wingspan | Primarily active at night, mating | Flying, reproduction |
Habitat and Distribution
Imperial moth caterpillars live in a variety of habitats across North America. They are usually found on trees such as oak, pines, and sweetgum.
Their distribution spans from Canada to the southern U.S., Mexico, and even the Florida Keys. In the U.S., they can be found from eastern Nebraska to central Texas.
- Oak trees: A common host for imperial moth caterpillars
- Pines: Another favorite host tree
- Sweetgum: Also frequented by these caterpillars
| Distribution Area | Examples |
|---|---|
| Canada | Forests and woodlands |
| United States (Eastern) | Eastern Nebraska |
| United States (south-central) | Central Texas |
| Mexico | Various regions |
| Florida Keys | Subtropical areas |
Feeding and Host Plants
Imperial moth caterpillars are highly adaptable when it comes to feeding. They are known as polyphagous insects, which means they can feed on various plants. Here are some examples of their host plants:
- Sassafras
- Oaks
- Maples
- Pine needles
Their feeding habits also depend on their life stage. The younger caterpillars tend to feed on leaves from:
- Maple leaves
- Pine needles
While the older caterpillars prefer:
- Oaks
- Sassafras
A comparison table of host plants and caterpillar preferences is shown below:
| Host Plant | Young Caterpillars | Older Caterpillars |
|---|---|---|
| Sassafras |  |
|
| Oaks | |
|
| Maples | |
|
| Pine needles | |
The different preferences of young and older caterpillars allow these insects to consume a variety of plant species, reducing competition for food resources.
Predators and Threats
Imperial moth caterpillars face various predators during their life cycle. Some notable predators include birds, mammals, and insects.
For instance, armadillos are known to prey on these caterpillars.
Despite being a nuisance, armadillos also play the role of predator in the ecosystem.
-
Pros of armadillos preying on caterpillars:
- Contributes to the natural balance of the ecosystem.
- Serves as a natural form of pest control.
-
Cons of nuisance armadillos:
- Causes damage to lawns and gardens.
- Carries the risk of transmitting diseases to humans and pets.
Caterpillars can protect themselves from insect predators through their physical features.
Long scoli found on young instars might provide them a level of protection.
Additionally, fumigants could pose a threat to imperial moth caterpillars.
Although they’re not specifically targeted, their habitat might be affected by fumigants used for other pests.
Keep in mind that fumigants come with their benefits and drawbacks:
-
Pros of using fumigants:
- Effective in controlling certain pests.
- Can reach hidden or inaccessible areas.
-
Cons of using fumigants:
- Potentially harmful to non-target species, like imperial moth caterpillars.
- Posing health risks to humans and the environment if not used properly.
Comparison of predators and fumigants:
| Feature | Predators | Fumigants |
|---|---|---|
| Target | Caterpillars1 | Specific pests |
| Eco-friendliness | Contributes to natural balance1 | May harm non-target species and the environment1 |
| Efficacy | Depends on the predator’s population1 | High efficacy when used correctly |
Conservation Status and Challenges
Imperial moth caterpillars face certain challenges and threats. One significant issue is the decline in their population. This can be attributed to several factors with specific examples discussed below:
- Endangered: Large mammals and carnivores often face endangerment, as illustrated in a study of the world’s largest carnivores.
- Insecticides: The widespread use of insecticides can negatively impact caterpillar populations by poisoning their food sources and directly harming the insects themselves.
- Lights: Artificial lights, such as streetlights and outdoor lights, can disrupt the natural behavior patterns and mating of nocturnal insects like the imperial moth.
Here’s a comparison table highlighting these challenges:
| Challenge | Description | Example Consequence |
|---|---|---|
| Decline | A reduction in population due to various factors | Loss of biodiversity |
| Endangered | Threatened with extinction due to external factors | Disappearance of species |
| Insecticides | Chemicals designed to kill insects can indirectly harm caterpillars | Reduction in food sources |
| Lights | Artificial lights can disrupt the behavior and mating patterns of nocturnal insects | Impeded reproduction |
Interesting Facts and Trivia
Imperial moth caterpillars are the larvae of the imperial moth, one of the largest and most beautiful moth species in the eastern U.S. Here are some interesting facts and trivia about these captivating critters:
- Imperial moth caterpillars belong to the family Saturniidae, also known as giant silkworm moths.
- While they are closely related to butterflies, moth caterpillars often display differences in behavior and appearance.
- There are various morphs within the imperial moth species, making each caterpillar unique.
Imperial moth caterpillars feed on a variety of host plants and are known to be adaptable. Some common hosts include:
- Oak trees
- Pine trees
- Maple trees
Due to their adaptability, these caterpillars can be found in diverse habitats, from deciduous forests to suburban areas.
Moth antennae are distinct from their butterfly counterparts. Moth antennae are often feathery, while butterfly antennae have a clubbed end.
A notable difference between butterflies and moths is their pupation process. Butterflies form a chrysalis, while most moths, including the imperial moth, spin a cocoon to pupate.
| Attribute | Imperial Moth Caterpillar | Related Butterfly Caterpillars |
|---|---|---|
| Antennae | Feathery | Clubbed |
| Pupation Process | Cocoon | Chrysalis |
| Hosts | Oak, Pine, Maple | Specific host plants |
Conclusion
In conclusion, the imperial moth caterpillar is a remarkable creature with various morphs and an adaptable nature. Its family, Saturniidae, encompasses other fascinating silkworm moths worth exploring.
These caterpillars can be found in various colors starting from light to dark green, orange to dark brown, and even nearly black.
Few species of caterpillars are known to deliver toxins through their spines or setae; However, thankfully, the imperial moth caterpillars do not fall into this category.
These magnificent creatures do not any significant threats to humans and are not venomous or poisonous. Use the information provided in the article to preserve their habitats and protect these beautiful caterpillars.
Footnotes
Reader Emails
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about Imperial moth caterpillars. Scroll down to have a look at some of them.
Letter 1 – Imperial Moth Caterpillar
Caterpillar
Sun, Nov 23, 2008, at 1:10 PM
Hello, I found this really cool caterpillar in my garden and I can’t find any pictures that match him it seems most are green. I live in central Florida and would like to know what it is and what it eats.
Any information you have would be great.
Thank you in advance!
P.S. My kids and I love your website!!!!
Felice Gilmartin
Central Florida
Hi Felice,
This is an Imperial Moth Caterpillar, Eacles imperialis. Most specimens of caterpillars of this species are green, but in order to better ensure the survival of the species, there are also blue-green, brown, and orange color variations of this caterpillar.
Many caterpillars change color right before pupation. Imperial Moth Caterpillars pupate in the soil, and we suspect this individual left the tree upon which it was feeding, and was searching for a nice plot of dirt in which to pupate when you encountered it.
Imperial Moth Caterpillars are not really fussy about their food. Specimens are found on a large variety of deciduous trees and they will even feed on some coniferous trees. Adult Imperial Moths do not feed.
Letter 2 – Imperial Moth Caterpillar
Imperial Moth Caterpillar
Hello, Bugman,
We were called to retrieve this charming fellow from someone’s yard. I had never seen an imperial moth caterpillar in real life before (I believe we’re at the very edge of the range), and was shocked at how enormous it was.
My mother isn’t a fan of bugs, and refers to the critter as “the crawling turd,” and is fascinated by its “Predator-like butt. I’ve placed the caterpillar in a container (12x6x12”) with a bunch of loose dirt.
At the moment, it’s just wandering around, but I’m hoping it will burrow down and pupate soon. I guess I’ll have to wait a few months to get a picture of the adult, barring infestation by tachinid maggots. Regards!
Emily
Hi Emily,
Thank you for sending your photo of the Imperial Moth Caterpillar accompanied by your mother’s colorful description.
Letter 3 – Imperial Moth Caterpillar
what is this thing?
we saw this bug/caterpillar today near our pond. it seems almost prehistoric. do you know what kind of caterpillar this is or what it will become? thanks,
jj
Hi JJ,
We have identified so many adult Imperial Moths this year, that it stands to reason we will be seeing plenty of Imperial Moth Caterpillars as well. Your image is the first to arrive. We currently have a photo of the adult Imperial Moth, Eacles imperialis, on our homepage.
Letter 4 – Imperial Moth Caterpillar
Largest Caterpillar I have ever seen!
Good day!
I have looked through your 3 pages of caterpillars, w/o success. Found this enormous caterpillar (well, I guess it is a caterpillar) in Midlothian, Virginia (near Richmond, Virginia). It was at least 5 inches long and very thick and hairy.
We camp and hike a lot and have never seen a caterpillar this size before. We didn’t keep it because we were afraid we would accidentally kill it, and of course, it’s gone now. Just very curious.
Have attached photos. I love your website! What beautiful critters you have there.
Thanks,
Sami
Hi Sami,
It is understandable that you couldn’t identify your caterpillar even though we have several on the site. This is an Imperial Moth Caterpillar.
They are usually green, sometimes blue-green, occasionally yellowish-orange, sometimes light brown, and then there is your example, dark brown, which is a color we have never seen.
The black horns are particularly noteworthy.
Letter 5 – Imperial Moth Caterpillar
I found this Caterpillar in the mulch at the preschool where I teach. It may make a good project for our classroom. But, I don’t know what kind it is. Also, whether it is safe to touch.
We are in Silver Spring Maryland. It looks kind of like a drawing I have of an Emperor Gum Moth Caterpillar. But, are those found in the U.S.?
Jennifer
Hi Jennifer,
There are several different color morphs of the Imperial Moth Caterpillar. It will metamorphose into a large beautiful yellow and purple moth. We have several images of adult moths on our Giant Silk Moth page.
Letter 6 – Imperial Moth Caterpillar
I was out checking my Leland Cyprus for bag worms and found this guy. Attached are 2 pictures of him. about 4 inches long green with yellow spots, yellow horns, and white hairs looks kinda like it had 2 heads, and black feet we are in Delaware
Chris
Hi Chris,
This is an Imperial Moth Caterpillar. Obviously, it doesn’t have two heads. The head end has yellow horns. We have gotten many, many adult moth photos this year, but this is just the second time for the caterpillar.
Letter 7 – Imperial Moth Caterpillar
Imperial Moth Caterpillar in Ontario
Hi Bugman,
Here is another picture of an imperial moth caterpillar taken last week in the Killarney provincial park. It seemed to be in need of cooling as it went halfway into the nearest lake before it came back to have this picture taken.
Its length was ~2.5″. Thanks for your nice collection of pictures even though the scientist in me is missing some structure on your site it still was the most helpful site I found in identifying my ‘bug’.
Carsten
Hi Carsten,
The letters on our individual pages are structured chronologically, and surely that must have some scientific value. We are reminded of that line in one of our favorite movies, “A Zed and 2 Noughts” by Peter Greenaway.
The two zoologists are visiting the zoo created by a young girl, and one remarks “Leave it to an innocent to put a spider and a fly together because they are both brown.”
His twin brother responds that “You can probably learn more about their behavior that way.” At any rate, we are artists, not scientists and we love your Imperial Moth Caterpillar image.
Letter 8 – Imperial Moth Caterpillar
Bugman,
My 2-year-old daughter found this out near her swingset today. We’ve only lived in coastal Virginia for 2 yrs so we’re not entirely familiar with local bugs. Can you help us to identify this character?
We don’t know what to feed him. It’s over 2 inches in length and very thick in circumference. Thanks.
This is an Imperial Moth Caterpillar. It will metamorphose into a lovely large yellow and purple moth.
Letter 9 – Imperial Moth Caterpillar
Hey BugMan!
Check out our Imperial Moth Caterpillar! This was found by a volunteer at our annual Beach Sweep River Sweep at Saluda Shoals Park. PS The Rangers love the site and use it a lot. Keep up the great work!
Jay Robinson
Interpretive Park Ranger
Saluda Shoals Park
Columbia SC
Hi Jay,
It thrills us to know that Rangers use our site. We are also very proud to have just received our own honorary Los Angeles Urban Rangers patch because of a talk we did at one of their rambles at the Los Angeles County Fair.
Your Imperial Moth Caterpillar is a fine specimen.
Letter 10 – Imperial Moth Caterpillar
Is it an Imperial Moth caterpillar? It’s the most similar identification I could do searching through What’s that bug? but I think that it’s just similar. Maybe they “come” in different colors, because my caterpillar is more red than orange (as those I could find in WTB?).
I found it in my backyard 2 days ago. I love nature, and it’s the first time I see one of these. If you can provide a name, I will look into it to find something more about these caterpillars and the moth/butterfly they will become.
Have more photos if you’d like, of detailed parts of its body. Just let me know. Thanks in advance!!! Great page, keep up the amazing work!
Esteban Ramallo
Hi Esteban,
You are absolutely correct. This is an Imperial Moth Caterpillar. We have gotten photos of brown, orange, and blue-green specimens, as well as your lovely green example.
Letter 11 – Imperial Moth Caterpillar
Wed, Oct 8, 2008, at 5:39 PM
The rangers at the tool shed at the Crater of Diamonds in southern Arkansas had captured this caterpillar and were asking everyone if they knew what it was.
I didn’t know, but I knew where to find out.
I hope this image is better than the one you have, but nevertheless, I turned them all on to your incredible site. Pic taken near the first of October.
Mike Green
Southern Arkansas
Thanks, Mike,
We don’t like to consider one image better than another, just different.
Same Individual, Different Submission???
Large caterpillar found at the park
Wed, Oct 8, 2008, at 12:57 PM
Large caterpillar found at the park
I work at a state park in southwest Arkansas and recently had a visitor bring in a very large caterpillar (about four inches long) he had found while exploring. Several people took photos of the beautiful specimen, and many offered guesses as to what it could be.
As my particular park is more geologically-focused, I regret to say I was not able to accurately identify the caterpillar for its finder. It was very lively, walking across our table, and had powerful legs and mandibles.
I released the caterpillar onto a sweetgum tree on the park premises. I have browsed through numerous photos, hoping to find exactly what type it may be. The closest I have come is a Luna moth caterpillar, but none of the photographs I have seen depict exactly the same features as this caterpillar.
Can you help out?
Waymon
Southwest Arkansas
Hi Wayman,
We have a sneaky suspicion that your co-worker Mike submitted an image of the same Imperial Moth Caterpillar. In the spirit of equity, we are posting both of your photos.
Letter 12 – Imperial Moth Caterpillar
Mon, Oct 13, 2008, at 5:29 PM
Hi, once again, I took this picture of this caterpillar in September, and of all the caterpillars that I have watched I have never seen one of these before, It is eating a pine tree.
It was about 4 inches long and as you can see in the picture it is green and yellow and hairy, and it seems to have little hands that it is holding the pine needle with while chewing on them, Is this a caterpillar or some type of larvae?
Is it dangerous? I have grandchildren that love to hold bugs. Thanks for any information.
Lisa Benningfield
Eastern Kentucky, USA
Hi Lisa,
Your photo of an Imperial Moth Caterpillar is quite beautiful. The Imperial Moth Caterpillar feeds on a wide range of trees, and it is the only caterpillar we can think of that eats deciduous as well as coniferous trees.
The adult is a large beautiful yellow and maroon moth.
Letter 13 – Imperial Moth Caterpillar
October 10, 2009
Photo taken 9/28/09 in the afternoon. He/she was crawling across the paved part of the Baldwin Rails to Trails from one side to the other.
Florida
Jacksonville, FL
Hi Florida,
This is an Imperial Moth Caterpillar.
Letter 14 – Imperial Moth Caterpillar
October 11, 2009
Found it crawling across my office’s parking lot during midday, 9/29/09, so it must have been looking for a spot to burrow into for pupating.
The office has many types of trees, including conifers.
Thanks to your awesome site, I was able to identify it and learn more about it.
Please feel free to use these pictures. I think they’re pretty good! There are 4 pictures I wanted to give to you, so I’ll send another message after this one with the 4th pic.
Be sure to check out the drool at the bottom of its mouth in the facial closeup! 
Thy Nguyen Cavagnaro – Barnegat, NJ
Jamesburg, NJ
Dear Thy,
Thanks for sending us your gorgeous images of an orange Imperial Moth Caterpillar. There are several different color variations for the Imperial Moth Caterpillar, including green, blue-green, and brown, and the caterpillar often changes color just prior to pupation.
This bright orange variation is not one of the variations we see most often and it is a lovely addition to our archives.
Letter 15 – Imperial Moth Caterpillar
November 1, 2009
this guy fell off a night-blooming cereus plant. 11/01/09. i put him in the pot and took a few more photos. when i checked on it 20 minutes later it was gone. buried in the pot maybe? will this be its ground-to-pupae stage? Will it eat the roots if this is indeed where it went?
Cathy Saunders
Longview Tx
Hi Cathy,
The only question we are able to answer for certain is to confirm that this is an Imperial Moth Caterpillar. Finding it on the cactus plant is unusual and we would not expect that it was feeding there.
It may have buried itself in the pot where it will not eat the roots (guess we answered a second question), but it may also have wandered off or fallen prey to some hungry bird or other predator.
Letter 16 – Imperial Moth Caterpillar
November 1, 2009
I found this big guy on a sweetgum tree and would love to know what kind he is. He’s very big and beautiful. Thanks
Martha
Lindale, TX
Hi Martha,
Your caterpillar is an Imperial Moth. After pupating underground, it will emerge as a lovely large yellow and purple moth.
Letter 17 – Imperial Moth Caterpillar
Location: Central Ohio
August 26, 2010, 6:26 pm
Is this a polyphemus moth caterpillar? He has four small yellow horns, so we are not sure. We saw him while hiking in Central Ohio in August. He was eating a maple leaf.
Hiker
Dear Hiker,
This may be the most beautiful image we have ever received of an Imperial Moth Caterpillar.
Letter 18 – Imperial Moth Caterpillar
Location: Accomack County, VA
September 18, 2010, 2:36 pm
Saw this big guy crawling up a tree in the woods near our house on the Eastern Shore of Virginia recently, and was wondering what it is. Fully extended, it was 4-5 inches long, and as big around as my thumb.
I’ve never seen one close to that size before. Any help on the ID would be appreciated. Thanks.
Signature: Linda C.
Hi Linda,
This impressive creature is the caterpillar of the Imperial Moth.
Another mystery is solved! Many thanks.
Letter 19 – Imperial Moth Caterpillar
Location: Wayne, PA
September 18, 2010, 5:32 pm
My daughter found this in a wooded area and gave it to me, and I have no idea what type of caterpillar it is.
I’m not sure what to feed it, or where to release it.
The first 2 pictures have a little more detail; the last picture shows the color a little more authentically. It’s kind of greenish-red. It’s big – about 3.5” long and about .75” ’tall’.
For some reason, we’ve been finding big caterpillars. First a tomato hornworm, then a hickory horned devil. Now this one, whatever it is.
Thank you!
Newstart
Signature: Newstart
Dear newstart,
This is the caterpillar of an Imperial Moth and we just finished posting another photograph of this species. Based on your individual’s coloration, we suspect it is getting ready to pupate.
Imperial Moths pupate underground, so when the caterpillars are ready to metamorphose, they climb down from the trees where they have been feeding and they locate an area where they can dig underground.
You probably don’t need to worry about feeding it because it is probably no longer interested in food. Release it on the ground in an area where the soil is not hard. We also just received a naked pupa of a Giant Silkworm Moth that might be an Imperial Moth, and we will post that letter next.
Mr. Marlos,
Thank you so much for the information. I released it near where it was found.
newstart
Letter 20 – Imperial Moth Caterpillar
Location: Warren County, New Jersey
September 11, 2011, 12:03 pm
On September 11, 2011, after many inches of rain, we saw this rather large caterpillar crossing the street near our house in Warren County, New Jersey. It was 3.25 inches long and about 1/2 to 3/4 inches wide.
I’ve never seen anything this large but I’m wondering if you could identify it for us. What will it turn into?
Signature: Curious in NJ
Dear Curious in NJ,
This Imperial Moth Caterpillar will bury itself to pupate and it will emerge as an adult Imperial Moth next year.
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