Promethea Caterpillar: All You Need to Know for Easy Identification and Fascinating Facts

The Promethea caterpillar is an intriguing species known for its unique appearance and remarkable development process. These caterpillars feed on a variety of plants, and their life cycle is one of astounding transformation.

Native to North America, the Promethea caterpillar is the larval stage of the Promethea moth, which boasts striking colors and patterns. Learning more about these fascinating creatures can inspire a sense of wonder and admiration for the complexities of the natural world.

Life Cycle of the Promethea Caterpillar

Eggs

The life cycle of the Promethea caterpillar (Callosamia promethea) begins with eggs laid by adult Promethea moths. These eggs are typically laid on host plants, including magnolia. Some characteristics of Promethea Caterpillar eggs include:

• Small size
• White to pale green color
• Laid in groups on the undersides of leaves

Caterpillars

After eggs hatch, larvae emerge and enter the caterpillar stage. Promethea caterpillars exhibit the following features:

• Growing through multiple instars (developmental stages)
• Color changes from yellow/green to black/blue with white spots
• Feed on host plant leaves

During this larval stage, the caterpillar consumes a significant amount of plants material and grows in size before transitioning to the pupa stage.

Pupa

At the end of the larval stage, Promethea caterpillars pupate. Important characteristics of the pupal stage include:

• Pupation typically occurs in late summer or early fall
• The formation of a cocoon using silk, leaves, and small twigs
• Overwinter as pupae in their cocoon before transforming into adult moths

Adult Moths

In the final stage of the life cycle, adult Promethea moths emerge from the pupae. Key attributes of this stage are:

• Mating and laying eggs to continue the population
• Male and female moths differ in color; males are brownish-black, while females have a grayish background color
• Adults have a wingspan of about 3-4 inches

Comparison table

Physical Characteristics

Appearance of Caterpillars

Promethea moth caterpillars have a unique appearance. They are known for their:

• White stripes
• Black polka dots
• Blue polka dots
• Bright red horns
• Yellow butt

These features make them easily recognizable among other caterpillars.

Color Patterns

Promethea caterpillars display distinct color patterns as they grow. Here’s a quick overview of their colors:

• Young caterpillars: Mainly black with white stripes
• Older caterpillars: More white stripes, black and blue polka dots

These color patterns help to identify their stage of development.

Adult Promethea Moths

When Promethea caterpillars turn into adult moths, their appearance changes significantly. Key characteristics of adult Promethea moths are:

• Wingspan: 3 to 4 inches in diameter
• Males: Dark brown with some red coloration
• Females: Lighter brown with beige coloring

Upon emergence, adult moths display a smiley-face emoticon on their wings, adding a unique touch to their appearance.

Interactions and Behaviors

Gregarious Nature

Promethea caterpillars are known for their gregarious nature, which means they tend to live and feed together. This behavior is mainly driven by the release of pheromones, which attracts other caterpillars and promotes aggregation.

• Pheromones: Chemical signals released by the caterpillars to communicate.
• Gregarious: Living and feeding together in groups.

Mimic and Defense Mechanisms

Promethea caterpillars have developed remarkable mimic and defense mechanisms to protect themselves from predators.

Mimicry

These caterpillars can resemble a twig, making them difficult for predators to spot. The resemblance to a twig serves as a protective camouflage, allowing them to blend in with vegetation.

Defense Mechanisms

Promethea caterpillars employ various defense strategies, such as:

• Displaying large eye spots on its body to mimic a snake or another predator.
• Exhibiting twig-like posture to minimize the risk of being detected.

Naturalists and researchers often study these intriguing behaviors of the Promethea caterpillar. By comprehending their interactions and behaviors, we can gain in-depth knowledge about the fascinating world of these caterpillars.

Distribution and Conservation

The Promethea caterpillar is the larval stage of the silk moth, belonging to the Lepidoptera order and the Saturniidae family. These caterpillars can be commonly found in the eastern United States, in habitats such as deciduous forests and mixed woodlands¹.

• Habitat: Deciduous forests and mixed woodlands
• Range: Eastern United States

Promethea caterpillars feed on a variety of trees, including:

• Wild cherry
• Tulip poplar
• Sassafras
• Sweetgum

Conservation of their habitat is essential for the survival of both the caterpillars and the moths. The U.S. Fish & Wildlife Service plays a crucial role in such efforts through habitat conservation planning.

Different features of the Promethea caterpillar and moth include:

• Caterpillar: Brown or green with noticeable eyespots
• Moth: Large, rusty brown or reddish-brown with darker markings

To better understand these fascinating creatures, let’s compare them with another species, the Cecropia moth, in a comparison table.

Protecting the Promethea caterpillar and moth is important for biodiversity. By conserving their habitat, we ensure a thriving ecosystem for future generations.

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 – Prometheus Moth Caterpillar

Unknown Silkworm with Tramp Stamp
Location:  Suburb North of Atlanta, GA
September 20, 2010 8:40 am
Your site has fed a hidden fire in me for a love of bugs. I commonly find myself crouched over colorful insects snapping pictures or discussing the creature with friends and neighbors…and strangers. :/ My reputation even led to the neighbors walking over Saturday to share their find. My 9yo believes this to be an early luna moth instar but I wasn’t sure if that was the right identification. I couldn’t find any images online that exactly matched this fat green guy. Can you help us? He’s about two inches long. I’ve included pictures of a close up on its ugly light colored face, its front, stumpy and back, sucker legs. So cool by the way! Are the back legs truly suckers or are those fine hairs I think I see that make the legs act like the mouth of a venus fly trap? My 4yo neighbor was just as enthralled as I was watching the back legs open and close. But I ramble…another picture I’ve included is of the awesome tramp stamp mother natur e gave this silkworm…a smiley face on it’s backside. Love it.
Thanks for all you do, bugman. You’ve helped us many, many times and hopefully you can let us know if my 9yo was correct or if this was something completely different.
Update: Looks like I can only include three pics, so I won’t be sending the ugly mug. If you need it for identification, let me know. The legs and tattoo are much more interesting.
Signature:  Resa

Hi Resa,
Your caterpillar is a Spicebush Silkmoth, also known as a Prometheus Moth or Promethea Moth, Callosamia promethea, which we identified on BugGuide.  We got a chuckle when you said you were attaching a closeup of the caterpillar’s head, because your photo is actually its rump.  Then we noticed your update that you were not attaching the head photo.  More information on this lovely moth can be found on BugGuide.

Letter 2 – Male Prometheus Moth

Male Promethea Moth
Location: S. Illinois
May 4, 2011 3:13 pm
My Promethea cocoon hatched out today. Unfortunately for my moth-herding ambitions, this one is a male.
He was released in the back yard, and is currently trying very hard to look like a dead leaf on a pine tree.
Signature: Bert

Hi Bert,
Though the coloration of the Prometheus Moth is quite somber, the markings are nuanced and quite beautiful.  The Prometheus Moth is a beautiful species.  We do not receive as many images of the Prometheus Moth as we do of other Giant Silk Moths, and we are very thankful though were thoughtful enough to provide your gorgeous photographs for our archive.

Letter 3 – Callosamia species laying eggs: Promethia Moth or Tulip Tree Silkmoth????

tulip tree silk moth?
Hello! I thought this picture was unique and wasn’t sure if it was a tulip tree silk moth- thanks for your help!
Catherine Pangan
Indianapolis , IN

Hi Catherine,
This is definitely a moth in the genus Callosamia, but we are unsure if it is a female Promethia Moth, Callosamia promethea, or a female Tulip Tree Silkmoth, Callosamia angulifera. Our inclination is that it is a Promethia Moth, but we want to try to contact a true expert, Bill Oehlke.

Letter 4 – Female Promethea Moth

help identifying this moth please
I’d love some help on this one! I live in NH and found this beauty on my house one morning around 9 am. Best regards,
Colleen L. Jones

Hi Colleen,
We believe with 95% certainty that this is a female Promethea Moth, Callosamia promethia, but the closely related Tulip Tree Silk Moth, Callosamia angulifera, is very similar. We found a Canadian Biodiversity website that has a side by side comparison of the two species. Males of the species are much smaller and darker.

Letter 5 – Female Promethea Moth

Subject: What bug is this?
Location: Yorktown, VA
June 28, 2014 6:09 am
Looks like some kind of butterfly or moth but the body and legs are strange!
Signature: Carmen

Hi Carmen,
We believe your Giant Silkmoth in the genus Callosamia is a female Promethea Moth and you can compare your image to this image on BugGuide.

Letter 6 – Female Promethea Moth, or close relative???

Moth ID
June 5, 2010
I would greatly appreciate an ID on these moths. The one looked like a cecropia, but I wasn’t sure. I know that patterns can vary considerably depending on location. Thank you!
Andrea
St. Peters PA

Hi Andrea,
Of the three species of moths in the genus Callosamia, we believe your specimen is a female Promethea Moth, Callosamia promethea, also called a Spicebush Silkmoth.  We are basing this on a photo posted to BugGuide. Our second choice would be a female Tulip Tree Silkmoth, Callosamia angulifera, also posted to BugGuide.  We will tackle your second moth separately.

Letter 7 – Mating Promethea Moths

Subject:  Cecropia Moths A-mating?
Geographic location of the bug:  Fayetteville, Georgia
Date: 05/05/2018
Time: 07:53 PM EDT
Your letter to the bugman:  Hi there! My mom and I spotted this fuzzy lady hanging out on our front doorway around noon on May 5, 2018. She stayed there all day long, and when I checked again a little after seven, I discovered she had company.
Thanks to your website, I think they’re Cecropia Moths? I’m just a little unsure because the male is so much smaller and darker than the female.
How you want your letter signed:  Lauren C.

Dear Lauren,
Though they resemble Cecropia Moths, your mating pair are actually Promethea Moths, Callosamia promethea, which are pictured on BugGuide.  According to BugGuide:  “Females come to lights but males do not” though we suspect an exception is that a male will be attracted to a female who was attracted to a light.  BugGuide also indicates an alternate name is Spicebush Silkmoth and states:  “larvae feed on leaves of apple, ash, basswood, birch, cherry, lilac, maple, sassafras, sipcebush [sic], sweetgum, tulip-tree; also recorded on buttonbush, magnolia, and other trees adults do not feed.”

Letter 8 – Mating Promethea Moths and resulting Caterpillars

Promethea ranching
Location: South Illinois
May 16, 2012 9:02 pm
Sent you a picture of a female promethea earlier this spring. She found a date, and now I’ve got about 40 caterpillars. Here is a picture of date night, and 3 instars of promethea caterpillar and one aphid.
Signature: -Bert

Hi again Bert,
We had your photo of this Promethea Moth and a Cecropia Moth together on the screen featured on our homepage for several weeks.  We are going to feature this submission as well in anticipation of drumming up interest in National Moth Week events from around the country.  You didn’t provide us with much additional information.  Your subject line indicates that you are raising the caterpillars.  Do you have them in a habitat?  Are they feeding directly from trees in your yard?  What trees are they feeding upon?  Young caterpillars feed in groups.  It is interesting that your photo shows three different caterpillar instars.  Are they from different parents?  We would expect that all eggs from one mating would develop at the same time.  Here is a photo from BugGuide that shows the socially feeding caterpillars.  Please provide additional information.

Update
May 17, 2012
All these caterpillars are from the same pairing. Don’t know if the slower-growing ones are sickly, or if this is a survival strategy, or if it is a result of how they are being fed. I keep them indoors in a terrarium with three baby-bottles full of tulip tree twigs harvested from around the neighborhood so I don’t make too big a hole in any one tree. One lesson learned so far is that the very young caterpillars like to go walkabout and if there is too much room in the tank and they will find a way to drown in all but the best-sealed water bottles, or get too far from a leaf and starve/dehydrate before they get back. Which is why I have about 40, instead of about 80. Attached are a few more bug pictures: group feeding, the cecropia from last month, and a small one for scale.

Thanks for the update Bert.

Letter 9 – Mating Prometheus Moths

butterfly
June 25, 2010
This pair of butterflies were found today on my backporch screen. I can’t identify them nor have I ever seen them before. They appear to be mating and they really haven’t moved in hours. Can you idetify them?
thefootballref
canfield, ohio

Dear thefootballref,
What a wonderful image of mating Prometheus Moths.  They exhibit pronounced sexual dimorphism, with the male being darker and smaller, and with a different wing shape.  BugGuide has an excellent profile of this Giant Silk Moth which is also called the Spicebush Silkmoth.

Letter 10 – Mating Prometheus Moths

Canoodling Saturniids
Location:  Western Pennsylvania (Slippery Rock)
August 27, 2010 9:26 pm
Hi, Daniel,
I am attaching two pictures of mating Saturniid moths, but I could not tell if they were Promethea Moths or Tulip Tree Silk Moths. You’ll notice from the file names that I first misidentified them as Io moths. About six weeks ago, these two were found on the screen over our mud room window, and there they stayed for many hours – literally most of the day. When night fell, they were gone. These are such elegant creatures.
Glenn Marsch

Hi Glenn,
These mating Prometheus Moths are truly lovely.  The moth closer to the camera is the dark male, and we suspect he looks larger because of the use of a wide angle lens which is distorting the perspective since the female is generally the larger of the sexes.

Wow, that was quick, and I am impressed.  Thanks for the ID.  Now I can go to my Flickr site & update the caption.
Best Regards,
Glenn

Letter 11 – Pair of Promethea Moths

Subject: Moth
Location: Erie, PA
June 18, 2014 5:47 pm
I found this moth outside my home in Erie, PA and am not certain what kind of moth it is.
Signature: Lindsey

Dear Lindsey,
We wish we could have responded in a more timely manner, but we were out of the office for ten days and we are still trying to  catch up on all the mail that arrived in our absence.  This is a pair of Promethea Moths, Callosamia promethea, or another member of the genus.  You can compare your image to this image on BugGuide.  The lower moth in the image is the female, and she is filled with eggs.  The male was attracted by her pheromones using his more feathered antennae to locate her.  Promethea Moths, like other Giant Silkmoths in the family Saturniidae, do not eat as adults, living only long enough to mate and reproduce. 

We suspect this gravid female Promethea Moth arrived first and the male was drawn to her.

Letter 12 – Promethea Caterpillars

Promethea ranching
May 23, 2012
Location:  South Illinois
4th and 5th instar. It is interesting having them staggered out like this. When I raised polyphemuses outside they were usually within a day or three of eachother developmentally. Keeping prometheas indoors I have a 2 week spread between the advanced class and the stragglers. Will be interesting to see if the slow ones will get there in the end.
Bert

Hi Bert,
Thank you for continuing to document your previous submissions.  We love seeing the result of the mating Promethea Moths that visited you this spring.

Letter 13 – Promethea Moth

Subject: Some beautiful close up photos of what I believe is a Prometheus moth
Location: Watkins Glen NY
May 20, 2012 3:17 pm
Hey there! I visit your site requently; as someone living in the ’country’ who was not raised here (raised in a relatively bugless suburban area), I have questions all the time about bugs I come across, and you are an awesome resource. Last night was our first night warm enough to be out on the deck late into the night, and I had visitor. A huge moth I’d never seen before. Took some photos and he was hanging out so relaxed I gently, without touching his wings, scooped him up- and he hung out on my hand for awhile, resulting in some cool pics. I was coming here to share them with you, and there on the front page was what I believe to be ’my’ moth lol, although mine is much more of a beautiful red. I hope you might be able to use these photos to show the beauty of this guy. And of course, if it is not a Prometheus moth, do let me know 🙂
Signature: MeganNY

Hi MeganNY,
We agree that this is a Promethea Moth, however, she is a female.  Males are much darker and have more feathery antennae.  The Promethea Moth can be distinguished from the similar Tulip Tree Silkmoth, according to BugGuide, by spots on the forewings: “Males are brown centrally, females yellowish brown. On females the angular white spots are largest on the forewings.”  On your moth, the spots on the hind wings are larger.

Thanks for getting back to me Daniel. Thank you for your confirmation and correction on her sex (I was just using ‘He’ as a generic descriptor, I had no idea either way). She actually hung out on our deck again yesterday for a few hours, fanning her wings… I’ll have to do a little more research on what she could be going. I’ve never seen such large and beautiful moths as these… gotta love living in the country! I also saw a big green moth later that night, but she only stayed a second and I wasn’t able to get a photo. I see on your site the Luna moth, I’m pretty sure that’s what she was.
Thanks again!

Letter 14 – Promethea Moth Caterpillars

Subject: Large Green Caterpiller
Location: Newburg, PA
August 5, 2017 3:16 pm
We discovered this caterpillar eating the leave of our tulip poplar tree. We don’t want them to destroy the tree as it’s a young tree we transplanted this spring. Can you identify them and is it safe to relocate them? I haven’t been able to find anything that looks similar. We are in south central PA and found these on August 5th.
Signature: Scott Lehman

Dear Scott,
Based on this BugGuide image, we believe your caterpillars are Promethea Moth Caterpillars, Callosamia promethea, or possibly a related species in the same genus.  According to BugGuide:  “larvae feed on leaves of apple, ash, basswood, birch, cherry, lilac, maple, sassafras, sipcebush, sweetgum, tulip-tree ; also recorded on buttonbush, magnolia, and other trees.  adults do not feed.”  There is no need to relocate them as they will not appreciably damage your tulip tree.  These individuals are nearly fully grown and they will soon stop eating and pupate.

Letter 15 – Promethea Moth Caterpillars: Third Instar

Subject:  Help identifying caterpillar
Geographic location of the bug:  Huntingdon, Pennsylvania
Date: 09/04/2017
Time: 09:04 PM EDT
Good Evening,
There are about 50 of these guys eating a bush in my backyard, can’t seem to ID them. Please help! Thanks.
How you want your letter signed:  Andrew Sharpless

Dear Andrew,
Based on this BugGuide image, you have encountered third instar Promethea Moth caterpillars.  Caterpillars pass through five instars or phases prior to pupation.  The first instar is marked by hatching from the egg, so your third instar caterpillars are half grown.  According to BugGuide:  “larvae feed on leaves of apple, ash, basswood, birch, cherry, lilac, maple, sassafras, sipcebush, sweetgum, tulip-tree (1); also recorded on buttonbush, magnolia, and other trees.”  Since you did not mention the type of bush, we are guessing you have no particular investment in it (meaning we are guessing you would know if you purchased a lilac or magnolia) and that you will let them develop.  Caterpillars rarely affect the health of plants they are feeding upon as leaves will generally regenerate.  The adult Promethea Moths are large and impressive, though not brightly colored.

Letter 16 – Promethea Moths Mating

Subject: Promethea Moth Buglove!
Location: Northeast Pennsylvania
May 31, 2013 11:49 pm
Hi Bugman,
Here is a snapshot of some Promethea Moths lovin’ on my porch. The female had camped out the night earlier and in the morning I found her alone in the same position. By mid afternoon, a male had landed and immediately they began to mate. To my surprise, this evening I found that our female had laid eggs already! This is all very exciting for me, and I hope that you will find these photos to be exciting too.
Love your site, thanks for all things bug-related.
Signature: Julianna in PA

Hi Julianna,
We do find your photos of mating Promethea Moths exciting.  Like other Giant Silk Moths in the family Saturniidae, Promethea Moths do not feed as adults.  The live as adults to mate and reproduce, so they cannot waste time.  The female cannot waste her energy flying around in search of a mate, so she often waits in a good location, perhaps near a food source for the caterpillars that will hatch from the eggs she lays.  She releases pheromones and attracts any males within the vicinity.  The caterpillars will begin to search for food upon hatching, and hopefully there will be “apple, ash, basswood, birch, cherry, lilac, maple, sassafras, sipcebush, sweetgum, tulip-tree” or even “buttonbush, magnolia, and other trees” nearby, as that is the list of food plants on BugGuide.

Letter 17 – Promethea Moths Mating and laying eggs

What kind of moth is this?
April 16, 2010
The reddish moth showed up two nights ago, and this afternoon I noticed she (I’m assuming she’s a she) had begun to lay eggs on a deck post. This evening the darker moth (the male?) landed next to her, and they seemed to connect at the thorax in bit of “nudge, nudge, wink, wink, say no more” moth love. I’ve found about four different moth identifications that could be this moth, but I’m curious what you think it is.
Michael
Landrum, South Carolina

Hi Michael,
What marvelous photos you have submitted.  These are mating Promethea Moths, Callosamia promethea, also known as Spicebush Silkmoths.  BugGuide has information on the identification of the species.  The female is the lighter larger moth, and the male is the darker smaller moth.  Your letter and wonderful photos almost got overlooked because it has the same subject line as a letter we posted the day before, and the archiving of our email system in WordPress combined them in our inbox.

Letter 18 – Promethea Silkmoth

Moth Swarm
We live in Northern Vermont and for the last several days we have had 50-75 individuals of the same type moth flitting around the outside of our house. Our inside cats are fascinated and our outside cat is batting them out of the air. Any help identifying and information on whether it is usual to see these numbers in one place would be appreciated. You can see our cat’s head in the corner of one of the pictures. Thank you,
Jerry Smith

Hi Jerry,
Due to the sheer volume of letters we receive and also due to our many obligations in life, we can only post a fraction of the mail and images we receive. Many factors govern our decision, but when we receive a high quality photo with a detailed letter of a new species for our site, it is a no brainer. This is the first Promethea Silkmoth image we have received though a caterpillar image did come our way in the past. The Promethea Silkmoth, Callosamia promethea, is one of the giant silkmoths. They are found in the Northeast portion of the U.S. aw well as Canada. Adults do not feed and live only a few days, long enough to mate. You were fortunate enough to witness a nuptial flight. The moths had synchronized biological clocks and this mass emergence must have been triggered by the perfect weather conditions.

Letter 19 – Prometheus Caterpillar

promethea moth, callosamia promethea?
These guys, about 2+ inches long and maybe as much as 1/2 inch in diameter, are eating our lilacs in southern Maine. Searching for “red spikes” “yellow horn” found only somebody else with the same question! Based on your site I went back to check Caterpillars of Eastern Forests again, this time finding the photographs. Pix at johncodygallery seem to confirm it. I guess you can’t tell the sex of the adult moth from the caterpillar? Or do they always go in pairs? Anyway I thought you might like a pic of these guys since I didn’t find one here already. Thanks – sounds like you just love doing this – lucky for the rest of us! (I do hope no new photos with 2005 dates mean it’s still early in the season, not that you’ve stopped – )
Debbie JKM

Hi Debbie,
We presume your websearch led you to our first Caterpillar page. We have a second as well with recent postings. You should also check out our homepage. Yes, this is a Prometheus Caterpillar. We don’t know how to tell the sex of the immature insect. Thanks for adding to our archive.