What Do Hickory Horned Devils Eat? A Friendly Guide to Their Diet

When you come across the caterpillar known as the hickory horned devil, you might find its appearance quite intimidating. However, despite its ferocious looks, these creatures are entirely harmless. As the largest caterpillar in North Carolina, the hickory horned devil can measure almost 5 inches long when fully grown. These vibrant caterpillars munch on a … Read more

Hickory Horned Devil: All You Need to Know in a Nutshell

The Hickory Horned Devil is a fascinating creature that you should know about. Known as the largest caterpillar in North America, this insect is the larval stage of the Regal Moth, scientifically named Citheronia regalis. Despite their alarming appearance, Hickory Horned Devils are actually harmless creatures.

You’ll most likely find these striking caterpillars feasting upon the leaves of various trees, such as walnut, hickory, pecan, persimmon, and sweet gum trees. They have a unique appearance, with their blue-green color and two pairs of yellow to orange curved horns just behind the head, as well as paired rows of spines down their back.

As the caterpillar matures, it can grow up to 12.5 to 14 cm in length, or about the size of a large hot dog. Their fascinating appearance and biological traits are what make the Hickory Horned Devil an intriguing species to learn about.

Hickory Horned Devil: Origins and Habitat

First Discovery and Classification

The Hickory Horned Devil (Citheronia regalis) was first discovered and classified in 1793. It is known for its impressive size and ferocious appearance. However, despite its intimidating looks, it is a harmless caterpillar.

Geographical Range

The Hickory Horned Devil can be found in various locations across North America such as:

  • Eastern United States
  • Central Florida
  • East Texas
  • Eastern Texas
  • Southeastern United States

The range also extends from Massachusetts and New Jersey down to Florida, reaching as far west as Texas and possibly extending into Mexico.

Habitat: These caterpillars are commonly found in areas where:

  • Hickory trees or walnut trees are present
  • Eastern hardwood forests are dominant.

Notable characteristics:

  • Caterpillars can grow up to 5.5 inches (14 cm) in length
  • They have a blue-green or pea green color
  • Their body has long, curved orange horns with black tips.

Examples of their preferred host trees are various species of hickory and walnut.

Physical Characteristics and Life Cycle

Distinctive Appearance

The hickory horned devil, Citheronia regalis, is a large caterpillar with a vivid appearance. Its color ranges from pea green to blue-green, and its back is adorned with rows of spines and two pairs of yellow or orange horns right behind its head [1]. The adult moth, called a regal moth, has impressive orange wings with narrow yellow bands and can have a wingspan of around 6 inches [2].

Some features include:

  • Pea green to blue-green color
  • Rows of spines and horns on back
  • Large size

Stages of Development

The life cycle of the hickory horned devil starts with eggs [1]. Once hatched, the caterpillar goes through several larval stages, growing and molting before reaching its full size of up to 5 inches long [3]. The larval stage lasts around 4-6 weeks [4].

Next, the caterpillar enters the pupation stage and forms a cocoon underground [4]. Pupation can last from 9 months up to two years, with some delaying emergence as an extra year insurance policy against catastrophes that can affect their generation [4].

Mating and Reproduction

After the pupation period, the adult regal moth emerges with its beautiful wings [2]. The adult stage is brief and primarily focused on mating and reproduction. Regal moths are nocturnal and therefore rarely seen [5].

Once mating has occurred, the female moth lays hundreds of eggs on the leaves of host trees like walnut, hickory, pecan, persimmon, and sweet gum [5]. The cycle then repeats as the eggs hatch into new hickory horned devil caterpillars.

Diet and Host Plants

Preferred Trees for Feeding

The Hickory Horned Devil, a caterpillar that eventually transforms into the Regal Moth, feeds on the leaves of various tree species. These caterpillars have a preference for:

Leaves and Nuts as Food Source

Leaves are the primary food source for Hickory Horned Devil caterpillars. They consume large quantities, enabling them to grow and molt several times before reaching their full size. This diet consists mainly of leaves from the preferred trees mentioned above, such as walnut, hickory, and pecan trees, along with persimmon and sweet gum source. Though nuts can also be found in some of these trees, the caterpillars do not consume them.

Comparison Table: Hickory Horned Devil’s Preferred Trees

Tree Genus Leaves as Food Source Nuts as Food Source
Walnut Juglans Yes No
Hickory Carya Yes No
Pecan Carya Yes No
Persimmon Diospyros Yes No
Sweet gum Liquidambar Yes No

These caterpillars play an essential ecological role by feeding on the leaves of these trees and causing them to shed earlier, which can help with the overall health and growth of the host plants. On the other hand, infestations can lead to defoliation and stress the trees. However, these caterpillars rarely reach population levels high enough to cause significant damage source.

Behavior and Interactions

Defensive Mechanisms and Deceptions

The Hickory Horned Devil (Citheronia regalis) is a unique species of moth native to North America. As the largest caterpillar in East Texas, some people might mistake it for a tiny dragon due to its appearance. Though it might appear ferocious, the hickory horned devil is actually harmless. Its spikes and large size serve as deceptive features to ward off potential predators:

  • Spikes: Present along the caterpillar’s body, these spikes may appear dangerous but are not toxic or poisonous.
  • Size: Its size, often compared to a large hot dog, can intimidate predators such as birds and snakes.
  • Coloration: The caterpillar has yellow spots that stand out against its green body, making it look more threatening.

Role in the Ecosystem

The hickory horned devil plays a crucial role in the ecosystem. As a caterpillar, it feeds on the leaves of walnut, hickory, pecan, persimmon, and sweet gum trees, helping control these plant species’ growth. It also serves as a food source for predators such as birds and snakes, despite its deceptive appearance. When it matures, the horned devil goes through a metamorphosis into the less commonly seen regal moth which is nocturnal. Additionally, since the adult moth has no functional mouthparts, it relies on the energy it stored as a caterpillar to sustain itself as it searches for a mate using pheromones with limited time.

Here’s a comparison between the hickory horned devil caterpillar and regal moth:

Feature Hickory Horned Devil Caterpillar Regal Moth
Size 12.5 to 14 cm Smaller than larvae
Colour Green with yellow spots Orange with yellow bands
Food Tree leaves Doesn’t consume food
Activity pattern Daytime Nocturnal

In short, the hickory horned devil is an important part of the ecosystem, providing a unique role as both a plant regulator and a food source for other species. Its deceptive appearance helps ensure its survival, allowing it to grow into the regal moth and contribute to its overall lifecycle.

Conservation Status and Human Impact

Threats and Challenges

The hickory horned devil, or Citheronia regalis, is a large caterpillar that turns into the regal moth, also known as the royal walnut moth. These insects live in deciduous forests and are drawn to:

  • Walnuts
  • Pecans
  • Buttonbush
  • Filbert
  • Persimmon leaves

They largely feed on leaves and meal from the mentioned plants. Although they are not considered rare, they face a few challenges:

  1. Destruction of their natural habitat
  2. Climate change
  3. Predators, like the cecropia moth

Importance and Protection

The hickory horned devil plays a vital role in their ecosystem. They are important for:

  • Plant pollination
  • Serving as a food source for other species

Protection efforts for these creatures are also important because they help maintain a balanced ecosystem. Regulated hunting and wildlife conservation efforts, such as the North American Model of Wildlife Conservation, focus on long-term management that benefits a wide range of species, including the hickory horned devil.

Preserving their natural habitats and implementing adaptive resource management processes are crucial steps for ensuring their survival. By protecting and conserving these insects, we contribute to the overall health and balance of their ecosystems.

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 – MYSTERY: Hickory Horned Devil, but IN AUSTRALIA?????


Subject:  Wierd looking bug appearedin my backyard
Date: 03/20/2021
Time: 01:49 AM EDT
Geographic location of the bug:  Australia, Victoria
Your letter to the bugman:  Hi! The other day this weird bug was eating my flowers so I carefully picked it up and put it on the sidewalk. Can you please try to figure out what it is?
How you want your letter signed:  Thanks, from TheBugQueen

Hickory Horned Devil: IN AUSTRALIA?????

Dear TheBugQueen,
Had you sent this email today, we would have thought for sure that you were pranking us on April Fool’s Day, but you sent this identification request in over a week and a half ago.  This is a Hickory Horned Devil, the caterpillar of the Royal Walnut Moth, but it is not native to Australia.  This species is native to eastern North America.  We have no idea how it got to Australia.  Perhaps there is a Saturniid fancier in your neighborhood who raised specimens and some escaped.  To the best of our knowledge, there are no known populations of
Citheronia regalis naturalized in Australia.  We are tagging this as a mystery.


Letter 2 – Moth Pupa: Possibly Regal Moth or Imperial Moth


Big Cacoon
Location: Southren WI
May 29, 2011 9:35 am
My Daughter found this in the woods behind our house (southren WI). She is a bug nut and asked me what it was. We have looked in several books but can’t figure it out. Its alive and moving and the topic of all talk at our house. We would love to know what it is.
Signature: Michael Roehl

Royal Moth Pupa

Dear Michael,
This is definitely a Moth Pupa and it is a large moth.  We do not believe it is a Sphinx Moth Pupa, though they bury themselves underground to pupate.  We are more inclined to identify this as a Giant Silkmoth Pupa, more specifically a Royal Moth Pupa in the subfamily Ceratocampinae, possibly an Imperial Moth or a Regal Moth.  Here is a matching photo of an unidentified Royal Moth pupa from BugGuide for comparison.  Here is a photo of an Imperial Moth Pupa from BugGuide and here is a photo of a Regal Moth Pupa from BugGuide.  You can see the similarities, though our inclination is to favor the Imperial Moth.  We love your photograph, especially the thoughtfulness of having the model change into an insect themed wardrobe.

Thanks so much for taking the time to help us out. My daughter is thrilled, who new you could have so much fun with a pupa. We have it in a “Critter Cage” if it hatches sucsessfully I will send you a picture.

Letter 3 – More Regal Moth Pupae


You wanted C regalis pupae photos? 🙂
Hi Bugman,
Love your site. I’m sure your comment that you don’t have many HHD pupae will prompt a flood, so I’m adding to it. I also have a couple of moths from Taiwan for ID I’m attaching: 1st: appears to be an Arctiid, tried searching with “clear winged” / “Taiwan” and did not locate anything. Location: Sun-Moon lake, Nantou county 2nd: attracted to lights at ~ 3000 ft. Location: Nantou county Thanks for your thoughts. Photos taken with Sony DSC-H2, auto, macro mode, cropped and resized with Microsoft Paint.

Hi Ray,
Your letter is so funny. We were hardly deluged with photos of Regal Moth or Royal Walnut Moth Pupae, but we did get two submissions. Your photo is wonderful. We have been very busy and are way behind in posting new submissions. We will try to address your Arctiid questions in the future.

Letter 4 – Citheronia splendens sinaloensis Caterpillar


Subject: Large caterpillar
Location: Southern AZ
August 19, 2017 10:04 am
We live in southern AZ had have these giant greenish gray (photo attachment) and tan version of this attached caterpillar on our AZ cotton. Are they the Horned devil caterpillar?
Signature: Len Nowak

Citheronia splendens sinaloensis Caterpillar

Dear Len,
You are quite observant to notice the similarities between your caterpillar and the Hickory Horned Devil, but that species is found only as far west as Texas according to BugGuide information.  Your individual looks so similar because it is a close relative in the same genus
Citheronia splendens sinaloensis, a moth with no common name.  The adult moth, which is pictured on BugGuide, is a darker, duller variation on the adult Royal Walnut Moth, the adult Hickory Horned Devil.

Citheronia splendens sinaloensis Caterpillar
Thanks Daniel
Besides the AZ horned devil….
We have amazing critters here at 4200′ in southern AZ.
A small sampling…
Signature:  Len Nowak

“Arizona Devil”

Thanks for the additional images Len.  The new “Arizona Devil” image is a wonderful addition to your previous posting.

Letter 5 – Hickory Horned Devil


He fell from the tree
Hi There!
This amazing Hickory Horned Devil Caterpillar fell from a tree onto our Brick steps yesterday. Before we actually knew what he was, he appeared quite vicious when probed, but after looking for him on the internet using the words HORNED and CATERPILLAR to search, we knew we had found our bug. Our daughter is facinated with him and so we kept him overnight, making a terrarium in a large bowl for him. He burrowed into the soil last night and she is now very sad. Our question to you is….while we captured him in a jar, he excreted a fairly large amount of brown liquid. Was this natural (excrement) or was this a neccessary fluid for pupation? We are worried that it may have been hurt during the fall. He fell a good bit of the way from the tree above, and like I said, onto BRICK. We don’t know if he is hurt or just pupating. Please help if you can. Thank You.
Beaufort, SC

Hi Lynn,
Hickory Horned Devils are rarely noticed until they drop from the trees to bury themselves underground where they pupate.

Letter 6 – Hickory Horned Devil


Hickory Horned Devil or Royal (or Regal) Walnut Moth Caterpillar Photo
Hi – My 8-year-old twins found this caterpillar on the street in front of our house (Aug. 21, 2008, Virginia Beach, VA) – we’re not sure what happened to it… Initially we thought he’d been run over (his mouthparts seem a bit damaged and there was liquid surrounding him – and very tiny ants were attacking him) but he didn’t really appear squished. We brought him in, rinsed off the ants and read a bit about him (which suggests that perhaps he fell out of a tree preparing to pupate and fell a bit too hard?) – and filled a jar with soft soil and what I hope are walnut leaves. He’s got a broken horn or two, and I’m not sure if he’ll make it (not sure what damage he’s sustained), but he is still moving around a little. Hopefully he’ll make it (we were afraid to leave him outside because the ants find him too attractive). Thanks for your site – my family and I use it almost every day to identify all the cool bugs in our yard!

Hi Monica,
Your Hickory Horned Devil would also be an attractive snack for birds and other predators. There is no way of knowing what caused the trauma. We received three images of Hickory Horned Devils today, and expect to get many more in the next month.

Letter 7 – Hickory Horned Devil: Third Instar


Hickory Horned Devil Variation?
I found this little beauty while walking around our farm on a photography stroll. The reddish/plum color caterpillar was on a sweetgum. I’ve looked around the .net and found no specimens that looked like this one….excpet for the Hickory Horned Devil. Could not find one unless it was green in color, but the markings and the horns were almost identical on some of the photographs I saw. Photo taken on September 3, 2007

Hi Jose,
This is a Hickory Horned Devil in its third instar. Caterpillars go through five instars as they grow, each time shedding their skin and changing appearance. In some species the change is quite dramatic. In two more molts, your specimen will be much larger and have the characteristic blue green coloration with red horns of the fifth instar, fully grown Hickory Horned Devil. BugGuide has a nice series of images from egg to final instar.

Letter 8 – Hickory Horned Devil: What's That Bug? "is much better than playing Playstation"!!!


Huge, Crazy Looking Caterpillar
Hi there,
Perhaps you can help. My son and I found this on Sunday, August 26, at a park in Irwin, Pennsyvlania. We almost stepped on this thing. We look for bugs all the time and have never seen anything like this. We did not keep it nor touch it. Do you know what it is? Sincerely,
Amy Vandermer and Mason (age 7)

Hickory Horned Devil

Ed. Note: Since we don’t have the time to post every submission that is sent our way, we sometimes just make a quick reply (see above). In this case, posting two additional images of Hickory Horned Devils in the past 24 hours prompted our decision not to post this letter. Then we got the following response, which is so endearing, that we rescued the original letter and photograph from the trash.

Thanks so much! Your Site is Awesome!
Thanks so much. We actually spent the rest of the evening on your website and found what the answer was. My son was so excited about your site after baseball all he wanted to do was look at bugs and drawn his own pictures. You might be happy to know that a 7 year old, second grader actually said . . . . . . “this is so much better than playing Playstation!” . . . his last words before bed were “after school tomorrow I’m coming straight home to identify more bugs!” You guys are awesome!

Letter 9 – Hickory Horned Devil


what is this?
Hey Bugman! My daughter and I saw this bug/worm (pic enclosed). Thought it may be a tomato bug but much larger than I’ve ever seen and what about the horns? Hope you can help. Thanks,
Brent Connors

Hi Brent,
The fierce looking but harmless Hickory Horned Devil is generally regarded as North America’s largest caterpillar. It has probably come down from the trees where it has been feeding so it can burrow into the ground to pupate, the next step in its metamorphosis into the lovely Royal Walnut Moth. We have had readers say the Hickory Horned Devil resembles a Chinese Dragon.

Letter 10 – Hickory Horned Devil


Can you help?
Hi. Please see attached photo. We found it in our woods and we have never seen anything like it. We were wondering if you could identify him and let us know what he will become. Its almost as big as my husband’s hand! Not sure what tree it was on. We have a lot of sweetgum and poplar. Thanks so much for your help.
Jennifer Poggemann
Southeastern Indiana

Hi Jennifer,
This is a Hickory Horned Devil Caterpillar. Several weeks ago we commented that we expected to see more requests for their identification this year because of the large numbers of adult moth images, the Royal Walnut Moth.

Letter 11 – Hickory Horned Devil: Early instars


Hickory Horned Devil
I’ve found your site to be a wealth of knowlege and information, which is a nice resource since i want to be an entomologist. Anyway, a friend of mine found an adult regalis at a light in mid-July in Maryland which laid eggs. I asked for a couple larvae when they hatched and she gave me 8 healthy 1st instar caterpillars on sweetgum. They of course grew, but i lost 4 while they were shedding into the next instar. Is this common with regalis? So i have four left, 1 third instar, 2 third about to shed into fourth, and 1 fourth instar. I also switched them from sweetgum to norway maple when they became third instars for convenience reasons. They LOVE it. I thought that you would like some pics of the larvae. I was also fortunate enough to land a female luna on August 10th. I have about 100 beautiful first instar larvae which i have feeding on my poor sweetgum sapling. I’ll send some pics of them when they get big enough.

Hi Josh,
Sorry that we cannot provide mortality rate information on Hickory Horned Devils. Thank you so much for providing images of early instar caterpillars for our site.

Letter 12 – Hickory Horned Devil: Early Instar


Large spiny caterpillar with horns?
We found this in our back yard and were unable to find it in any of our guide books. Then we searched online and found nothing. Can you tell us what it is? More curious about what it is going to be?? Thanks so much Sincerely
the Braun family in Fredericksburg Virginia

Hi Braun Family,
This is an early instar of the Hickory Horned Devil. What it will be after a few more molts is North America’s largest and quite possibly most impressive caterpillar. It will become a bright blue-green behemoth with red horns that resembles a Chinese dragon. The adult moth is also quite striking. It is known as the Royal Walnut Moth or Regal Moth, Citheronia regalis.

Letter 13 – Hickory Horned Devil


Large Horned caterpillar
We found this caterpillar on a tree in our yard. We live close to Houston, TX and have never seen a caterpillar this large before. Can you identify it and let us know what it is?
Marlys Dow

Hi Marlys,
The spectacular Hickory Horned Devil will become the equally spectacular Royal Walnut Moth.

Letter 14 – Hickory Horned Devil: First Submission of the year other than hatchlings


Is this a cousin to the Hickory Horned Devil?
I found this on my driveway and cannot determine what type of Caterpillar it is. It looks like the Hickory Horned Devil, but, is smaller and yellow. Do you have any idea what it is, and what it will turn into?

We are not upholding our recent threat to directly trash all letters without locations for the simple reason that we are delighted to be posting our first Hickory Horned Devil of the year. It is a wonderful photo. The fact that you found this Devil on the ground instead of a tree indicates it is probably getting ready to pupate. Just before pupation, many caterpillars change colors. We expect to receive many more images in September.

Sorry about that. I live in Herndon Virginia.

Letter 15 – Hickory Horned Devil


Can you identify this?
Found under the shrubs in my neighbor’s yard in North FL.
The shell and spines are hard, it seems aggressive when you get near it. The quarter is for size approximation.

Hi there Joe,
The caterpillar of the lovely Royal Walnut Moth is the fierce looking but harmless Hickory Horned Devil.

Letter 16 – Last Year's Hickory Horned Devil


Thought I’d share…
I stumbled across your website while doing some research on sand wasps and I figured you should have one of my pictures! It’s a Hickory Horned Devil caterpillar. I found it last year at the day camp I work at and thought it was the coolest ever! Hope you all can use it.
Simon Mahan

Hi Simon,
We usually get our Hickory Horned Devil photos in September. We just got an image of the adult Royal Walnut Moth this week. Your photo will be a nice prelude to this year’s images. Thank you.

Letter 17 – Hickory Horned Devil


heres a pic for you
I didnt know how to upload a photo to your site, so i hope this is ok. We have been everwhere on the internet, tring to find what this caterpillar was called. And thanks to your site we now know. I hope you can use the picture. I have a few more if you would like them. Thanks again.
bbscarvic and family

Hi BB,
Thanks for your head-on view of a Hickory Horned Devil. The time and effort we spend posting all letters and images ourselves allow us to control content as well as aesthetics. Thanks for your contribution.

Letter 18 – Hickory Horned Devil


Again, this is a catepillar encountered on a dry riverbed at the Walls of Jericho in Tennessee.
It’s about six inches long and one inch wide.

We misplaced your original email which happens when photos are not attached to the text. This is a Hickory Horned Devil. There was one on our homepage if you had looked.

Letter 19 – Hickory Horned Devil


caterpillar photos
Hi there fellow bug lover,
Thought you might like these photos that I took yesterday. I’m a horticulturist at a garden center in Lake Charles, LA. A customer came in with this wonderful Hickory Horned Devil specimen to see if we could identify it for her. It had been devouring her pecan tree. She was pretty concerned because we had already lost so many large trees last year to Hurricane Rita. I gave her the link to your website and advised her to let big ol’ “George” free to resume fulfilling his ravenous appetite…preferably far back in the woods behind her house. He was really a beauty! Hope you enjoy the photos.
Lu Hoffman
Landscape Maintenance Manager
Greengate Garden Center

Hi Lu,
We have already decided to profile the Hickory Horned Devil as the Bug of the Month for September.

Letter 20 – Bug of the Month: September 2006 – Hickory Horned Devil: first of the season!!!


hickory horned devls
Dear Bugman,
I have three awesome, fearsome-looking hickory horned devils devouring a small sumac tree on my property. My best friend in town is actually an honest-to-goodness entomologist, and he showed me what the adult royal walnut moth looks like too. It would be a privilege to see the lovely adult morph next spring. The caterpillars are probably 5 inches long now-I’ve been watching them for a week or so now. My kids, and especially my two girls, think they are the coolest bugs what ever were. I’ve attached two pictures of them to this email. Enjoy them or post them as you see fit.
Glenn A. Marsch
Physics guy, Grove City College
P.S. When do the moths leave the pupa, and is there any way I might attract the adult moth, or know better how to find them?
P.S.S. Great website! Thank you!

Hi Glenn,
We are so excited to get the first Hickory Horned Devil photos of the season. We usually get the final caterpillar instar images in September when they turn green and leave the trees to pupate. We have been considering the Hickory Horned Devil for the bug of the month for September and would like to request an additional photo once your tenants turn green. BugGuide has an excellent documentation of the caterpillar from egg through several molts. The adults emerge in June and July judging by the identification requests we receive at that time. You probably don’t have much of a problem attracting the adult moths since you have caterpillars on your sumac. Adults do not eat, and the only way to attract them is with pheromones from the female and with food plants. Thanks again for the wonderful contribution.

Dear Bugman,
Now you’ve gone and done it. My scientist mode has kicked in and I thought I’d take pics of the hickory horned devils every other day to see how they morph. The caterpillars are 4.5 inches long, not 5.0–I had my daughter Betsy measure the one stretched lengthwise on the sumac leaf rib (“hickory horned devil 8-21 B”). They do seem to be greener. They have moved from leaf to leaf and if they don’t pupate for a few weeks, they might denude the whole branch of that small sumac sapling. I have noticed that they are frequently found hanging halfway off the rib of the composite sumac leaf, as you can see in the second photo, “hickory horned devil 8-21 d.” If it bugs you (pun sorta intended) for me to send you too many photographs, I’ll stop, I promise. I do think these things are wonderful. We’re trying to observe without disturbing them, which so far seems to be working, because they’re getting as fat as Heimlich in A Bug’s Life–we sure aren’t putting them off their feed. Again, feel free to use any of these photographs. If you do post them on your website, and if you credit them (I really don’t care), could you please credit them to Steve Jenkins and Glenn Marsch. Steve is the entomologist at Grove City College who identified them for me. We’ve had a great time watching them. Cheers,

Hi again Glenn,
Your new photo is gorgeous, and there has been a molt between now and the previous image. Both of us are photography instructors and your photos are quite excellent. As we already said, we are contemplating the Hickory Horned Devil as the Bug of the Month for September. If you do not get us a better photo, and we expect you will (we are notorious for pushing our students to the limits of their potential) then we will use your most recent photo as the Bug of the Month image, but will need to edit your letters slightly. Thanks so much

Hi, Daniel and Lisa Anne,
Thanks very much indeed for your kind comments regarding my photographs. I appreciate you adding one of my photos to your caterpillar page. I’m not a trained photographer and I don’t have fancy equipment, but I do try to compose my photos as best I can. Beauty is sometimes a rare thing in this world, but I try to see it where I can, and even mathematical physicists use standards of beauty in their theories: a spare, severe kind of beauty, perhaps, but beauty nonetheless to those trained to see it. (I’m not a mathematical physicist!) It’s raining here today but I’m going to try to get a few more pictures of the hickory horned devils this afternoon. I will do my best to up the ante and take better photos than the last ones!

Letter 21 – Hickory Horned Devil


I love your site and the Hickory Horned Devil
Dear Bugman…
A fellow insect enthusist friend of mine sent me your site and I just love it! I photograph critters in my yard all the time. Some furry, some scaled, most are insects. Most of the time I can figure out what they are. Sometime I can’t. Now I know where to check! I am in love with the giant silkmoths of the night. Some years back I came across a Hickory Horned Devil for the first time, who had quite an adventure with me. I made a webpage about my HHD and thought you’d really like to see it. I’d love for you to share it with your readers to learn more about the HHD and the Royal Walnut/Regal Moth.
I get messages every year around late Summer/early Fall from all over the country from people that found one. I’m especially excited when children email me to thank me for my webpage’s info on the HHD. I’ve had many children use my page for reports in class. I think it is very important to edcate the importance of insects at a young age. Too often, innocent creatures are killed because of ingnorance. Which leads me to my appreciation for your “Unnecessary Carnage” section. Thank you for infoming people that killing insects is completely unnecessary much of the time. I frequently will grab a roach or even a wasp from indoors with my bare hands and put it outside. Oh, I’ll be sending you photos for your “Bug Love” section at some point too. Thanks again for what you do…
Jana Miller – The Nature Coast, Florida

Hi Jana,
Thank you for your sweet letter. We will post a link to your site. We have gotten so many photos of Royal Walnut Moths this summer, including a mating pair, so we expect it to also be a very good year for siting the Hickory Horned Devil.

Letter 22 – Hickory Horned Devil


I would like to provide you with decent photos of the “Hickory Horned Devil”
I thought you may like a nice shot of this little critter (well, since its the largest in America, he’s not so little)
Anyway, Thanks for the info, you guys are how I found out what this guy was!! Please, if you can, reply so I will know where to go see my pics, if you use them!! Thanks again!br> Tasha L. Holden
Powder Springs, GA

Hi Tasha,
When we first post letters, on an average of 4 per day, they go to our homepage at www.whatsthatbug.com and afterwards, they are added to the extensive archive devoted to more specific pages. You will continue to find your letter and image on Caterpillars 7.

Letter 23 – Hickory Horned Devil: Early Instar


Are you still identifying bugs?
I’m not sure if you’re still identifying bugs or not, but there is a spectacular looking caterpillar that arrived on my balcony a few days ago, and I’d like to know more about it. If it helps in the identification, I live just outside Atlanta, Georgia. Normally my cat eats the bugs on the balcony (mainly roaches…thanks, kitty), but both times kitty put her paw to the back of this caterpillar, it reared up. For some reason, that made kitty leave it alone. I wondered if maybe the spines were irritating or her paw (because surely she wasn’t threatened by that). Also, I’m wondering whether I should perhaps move the caterpillar back down to where the leaves and plants are. I’m on the 3rd floor of an apartment building, and there is no caterpillar food on my balcony. Thanks for any information and advice you can offer,

Hi Krista,
This is an early instar of our featured Bug of the Month, The Hickory Horned Devil. The caterpillars molt four times before attaining their full size, the fifth instar right before pupation. Earlier instars are brown, not green. We believe this is the third instar as shown on BugGuide.

Letter 24 – Hickory Horned Devil: First example this year


What’s that bug
I almost stepped on this one in my backyard, just north of Atlanta, Georgia. I let it go back in the woods after I took this picture. What’s that bug? Thanks,
Adam Kirkley

Hi Adam,
This is a Hickory Horned Devil, the caterpillar of the Royal Walnut Moth. This is very early in the year for this caterpillar. We get numerous photos each year, generally in September.

Letter 25 – Hickory Horned Devil


Strange Variation of HHD
Hi. I ran across your site as my three year old and I are trying to put a name to some of the tiny creatures around our Florida home. I have seen the Hickory Horned Devil Catapillar many times but none of them look like ours. Please tell us if we have a true HHD or something else. Thanks so much. (See attached.)
Have a blessed day!
Jacilyn Wheeler

Hickory Horned Devil
Hickory Horned Devil

Hi Jacilyn,
Your Hickory Horned Devil looks like a normal fifth instar caterpillar. Perhaps those you saw previously were younger caterpillars, but as you did not describe the difference, we are uncertain. At any rate, it is wonderful to have your gorgeous, yet typical, Hickory Horned Devil to add to our archives. As we are currently transitioning our site, the image will not go live until we finish the site migration.

Letter 26 – Hickory Horned Devil: First sighting of the season


8 inch black-spiked, green bodied, red horned Dragon Caterpillar
August 17, 2009
I found this huge creature in my Virginia Beach grassed yard.
F. Davis
Virginia Beach, Virginia

Hickory Horned Devil
Hickory Horned Devil

Dear F. Davis,
Despite the blurriness of your images, the Hickory Horned Devil is immediately recognizable.  The Hickory Horned Devil, along with other stunning insects like the Luna Moth and Dobsonfly, always thrill us when we receive the first photos of the season.  The Hickory Horned Devil is the caterpillar of the equally stunning Royal Walnut Moth.  Though 8 inches is something of an exaggeration, the Hickory Horned Devil is an enormous caterpillar.  It is perfectly harmless.

Letter 27 – Hickory Horned Devil


horned caterpiller
August 24, 2009
Some friends and I were taking a walk in Hemlock gorge in Maryland and we came across a very strange caterpiller. It was on a chunk of tree bark which was on top of a large rock in a stream.
Hemlock Gorge Maryland

Hickory Horned Devil
Hickory Horned Devil

Hi Jason,
We always enjoy posting the first Hickory Horned Devil photographs of the season, and your photo is neither the first nor the second we received, but it is the most detailed.  Thanks for sending us this gorgeous Hickory Horned Devil photograph.

Letter 28 – Hickory Horned Devil


September 1, 2009
BRICK, NJ 08724

Hickory Horned Devil
Hickory Horned Devil

Though it looks quite fierce, the Hickory Horned Devil, the caterpillar of the lovely Royal Walnut Moth, is quite harmless.

Letter 29 – Hickory Horned Devil


Damselfly or not?
October 13, 2009
I found this bug at my grandma’s house. At first I thought he was a dragonfly. He’s brown and has multiple wings. My mom thinks he is a damselfly. Can you help us? also, I am sending 2 pictures of a garden spider and Hickory Horned Devil.
McAlpin, Florida

Hickory Horned Devil
Hickory Horned Devil

Hi Scarlett,
We already wrote back to you to tell you that the damselfly is actually an Antlion.  In trying to select letters for posting today, we would much rather post your photo of the Hickory Horned Devil since we did not receive as many nice photos of this spectacular caterpillar as we have in past years.

Letter 30 – Hickory Horned Devil


Square Eyed Hornworm
May 29, 2010
Found this amazing and ugly fellow on a Vitex agnus-castus nibbling away. He was up high in the tree and I only saw one. It is May in Wharton, Texas. He is between 3 1/2″ and 4″ long. I haven’t a clue. I wish I was a better photographer. My neighbor took some pictures – if I get them (and they should be better) I will send them on. I looked through all of your hornworms and didn’t see him, but then again, maybe he isn’t a hornworm. Thanks so much for this site. I have used it sooooo many times.
Wharton, Texas

Hickory Horned Devil

Hi Carolyn,
This is extremely early in the year for us to receive a photo of a Hickory Horned Devil, the caterpillar of the Royal Walnut Moth.  Typically, we get the first Hickory Horned Devil photos around August.  The Hickory Horned Devil is not a Hornworm, but a rather one of the Silkworm Moths.

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The hickory horned devil caterpillar is a fascinating and unique creature in the world of insects. As the largest caterpillar in North America, it can grow up to six inches in length, making it an interesting subject for nature enthusiasts. The hickory horned devil is the larva of the regal moth and feeds on various … Read more

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The hickory horned devil, scientifically known as Citheronia regalis, is a remarkably large caterpillar with an intimidating appearance. Although this creature might seem threatening, it’s important to note that it is actually harmless to humans. Found commonly feeding on leaves of walnut, hickory, pecan, persimmon, and sweet gum trees, these sizable caterpillars are intriguing subjects … Read more