The imperial moth is a fascinating and visually stunning creature. As one of the largest and most beautiful moths in the eastern United States, it’s definitely worth learning about. From the moth’s striking appearance to its unique preference for being stationary, here’s what you need to know about the imperial moth.
Adult imperial moths can have an impressive wingspan of four to five inches, with the females being slightly larger than the males. Their beautiful yellow wings are adorned with various red-brown spots, making them hard to miss during their nighttime flights. One interesting fact about these moths is their relative lack of movement, as they remain pupae in the soil throughout the winter months, emerging in June or July as fully-grown adults source.
In their caterpillar stage, imperial moth larvae can grow up to a staggering 5.5 inches, while displaying a wide range of appearances. They can be found in different shades of green or brown, depending on their environment source. These caterpillars also possess intriguing features such as four spiny horns on their thoracic segments, further adding to the moth’s unique nature source.
Imperial Moth Basics
Eacles imperialis, commonly known as the imperial moth, is a stunning species of moth. This large insect belongs to the Saturniidae family, specifically the Ceratocampinae subfamily.
- Size: Imperial moths can have a wingspan of 4 to 5 inches.
- Color: They have yellow wings covered with red-brown spots and, occasionally, purple markings.
- Antennae: Males have more feathery antennae compared to females.
Distribution and Habitat
Imperial moths are widely distributed across the eastern US and parts of Canada. Their range extends from southern New England to the Florida Keys, and west through the southern Great Lakes region to eastern Nebraska and central Texas. However, they have retreated from some areas in the mid-twentieth century.
- North America: They can be found in eastern regions of the US and Canada.
- Subspecies: Different subspecies inhabit specific areas.
- E. i. imperialis: Eastern US
- E. i. pini: Rocky Mountains
These moths prefer deciduous or mixed forests and can also be spotted in suburban areas with plenty of trees.
Life Cycle of the Imperial Moth
Imperial Moth females lay their eggs on the foliage of host plants, which include:
- Box elder
- Norway spruce
- Honey locust
These eggs hatch into larvae that eventually grow into different stages called instars.
The Imperial Moth caterpillar varies in appearance; they can be either:
- Green form (light to dark green)
- Brown form (orange to dark brown or nearly black)
Caterpillars have several notable features:
- 4 spiny horns in the front
- Black bands along the body
- Large size, up to 5.5 inches
These larvae feed on host plant leaves, such as pine needles and elm leaves. As they go through the various instars, they face various predators, like birds and other insects.
Once the caterpillar reaches its final instar, it pupates in the soil by burrowing and forming a cocoon. The pupal stage occurs throughout the winter months. During this time, the moth undergoes significant development within the safety of its chrysalis.
The beautiful Imperial Moth emerges from the cocoon during June or July in the adult stage. Key characteristics of the adult moth include:
- Wingspan of 4 to 5 inches
- Female is slightly larger than the male
- Bright yellow wings with red-brown spots
Adult moths are primarily nocturnal, making flying and mating their main activities at night. The decline in the population of Imperial Moths has been attributed to factors such as deforestation, insecticide use, and environmental changes.
Comparison between Caterpillar and Adult Moth
|Size||Up to 5.5 inches||4-5 inches wingspan|
|Color||Green or brown form||Yellow wings with red-brown spots|
|Predators||Birds, insects||Birds, bats|
|Feeding Habits||Feeding on host plant leaves||Adults do not feed|
Threats and Conservation
Imperial moth caterpillars face predation from various animals, such as armadillos (Dasypus novemcinctus), which may trap and eat them. Other predators include:
Pesticides and Their Impact
Pesticide use in the mid-Atlantic region poses a threat to imperial moths. Pesticides designed to target pests like silkworm moths may also harm non-target species like imperial moths. For example, pesticides can:
- Damage their habitat
- Kill caterpillars or adult moths directly
Steps for Conservation
Conservation efforts by the Fish and Wildlife Office could help protect imperial moths. Some steps to consider are:
- Reducing pesticide use, or using eco-friendly alternatives
- Preserving and restoring habitats
- Raising awareness about the importance of moths in ecosystems
Comparison table for potential conservation steps:
|Reduce pesticide use||Protects non-target species; eco-friendly||Could lead to increase in pest populations|
|Habitat restoration||Provides new homes for threatened species; biodiversity||Can be time-consuming and expensive|
|Raise awareness||Encourages public involvement; supports policy changes||May not directly impact moth populations|
Imperial Moth Behavior
Attracted to Light
Imperial moths, like many nocturnal insects, are attracted to lights. This behavior is commonly observed in rural and suburban areas. For example, it is not unusual to find an imperial moth flying towards a front porch light or hovering around a well-lit storm door at night.(source)
Mating and Reproduction
When it comes to mating and reproduction, there are some key differences between male and female imperial moths.
- Female moth: Slightly larger than the male, with bright yellow wings covered in red-brown spots and a diagonal red-brown line across all four wings. (source)
- Male moth: Smaller than the female, with more feathery antennae. (source)
Imperial moths lay their eggs on the foliage of host plants. The caterpillars can grow up to 5.5 inches and display a variety of colors, ranging from light green to dark brown. (source)
Here’s a comparison of the two types of caterpillars:
|Green Form||Brown Form|
|Ranges from light to dark green||Ranges from orange to dark brown to nearly black|
|4 spiny horns in the front||4 spiny horns in the front|
In conclusion, imperial moths are fascinating creatures with unique behaviors, such as their attraction to lights and differing appearances in mating and reproduction. These large, colorful insects are an interesting aspect of wildlife in areas across the eastern U.S. and as far west as the Atlantic Ocean.
Caterpillar Diet and Host Plants
Common Host Plants
Imperial moth caterpillars, scientifically known as Eacles imperialis imperialis, feed on an array of host plant leaves, which are crucial to their growth and survival. Some common host plants include:
- Norwegian spruce
These caterpillars exhibit a preference for certain tree leaves. For instance, they find maple leaves, particularly sugar maple and boxelder, to be especially appetizing.
When comparing tree leaves of oak and pine, oak tends to be a more favored option for the imperial moth caterpillars. However, they can adapt well to the available host plants in their environment.
|Preferred Leaves||Less Preferred Leaves|
|Maple (Sugar, Boxelder)||Pine|
Some key characteristics of imperial moth caterpillars include:
- Furry appearance
- Large size (up to 5.5 inches long)
- Diverse color patterns
It is worth noting that these caterpillars are nocturnal, meaning they are more active at night and attracted to artificial lights.
In conclusion, imperial moth caterpillars feed on a variety of tree leaves, with preferences for maple and oak leaves. They possess distinct characteristics and are fascinating creatures to study and observe.
Molting and Instars
Imperial moths belong to the Saturniidae family and undergo several stages of development, including molting and growth through instars.
Molting in insects is the process of shedding their old exoskeleton to make way for new growth. As imperial moth caterpillars grow, they move through five growing stages or instars. Each time they grow too big for their skin, they will molt and enter the next instar stage.
Imperial moth caterpillars may change appearance and coloration as they molt, such as becoming darker in color. They can range from light to dark brown, burgundy, or green. Full-grown imperial moth caterpillars can reach a size of 75-100 mm (approximately 3-5½ inches) in length.
During the larval stage, imperial moths use different plant species as their food source, including eucalyptus, potentially affecting their development. Different factors, such as temperature and overwintering conditions, may influence the molting process as well.
If the molting process gets interrupted or the caterpillar becomes damaged, it may result in a deformed moth. In some cases, mold might develop on the caterpillar’s skin, causing it to appear moldy. To prevent harm to these moths, it is essential to use humane techniques to move them if needed.
Imperial moth caterpillars can be found along the Atlantic coast, and their appearance may vary with dark crossbands and black bristles. They typically only have one brood per year.
In conclusion, the molting process and instars are crucial stages in the development of imperial moth caterpillars, with several factors influencing their growth and appearance. By understanding these processes, we can better appreciate and protect these remarkable creatures.
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 – Male Imperial Moth
Eacles Imperialis (Royal Moth)
Hello Bugman! I took photos of a really cool moth. After 3 hours of research, I found that it’s a type of imperial moth called eacles imperialis using the bugguide.net online, then doubled checked over at lep-barcode. It lives on pine trees, which is abundant near my home, bordring the Pine Barrens National Forrest in NJ. I didn’t see any like it on your site, but maybe I missed it.
Your male Imperial Moth photo is great. Female Imperial Moths have more yellow on the wings and males have more markings. We actually have quite a few photos of this species including the mating pair we have had on our homepage for about a week.
Letter 2 – Male Imperial Moth
Subject: Imperial Moth
Location: South Carolina, an hour north of Columbia
July 21, 2012 4:43 pm
I thought I would share with you a photo of this Imperial moth that my family and I and some friends of ours came across on the way back from our vacation in Charleston, SC. It was at a rest stop about halfway between Columbia, SC and Asheville, NC. It is one the the most beautiful moths I have ever seen. I hope you enjoy the pic! Sorry its not better quality. It was taken with my Android phone. Feel free to rotate or crop to make it fit better on your site. Thanks for all you do! Your website is amazing!
Thanks for sending us your photo of a female Imperial Moth and thanks for the compliment.
Thanks so much for posting my photo. I thought this was a male though, honestly. I thought females were more yellow. I’ve always read that males have more purple.
Thanks for catching our error.
Letter 3 – Male Imperial Moth
5 1⁄2 inch wing span. Back porch. Austin Texas. We have Cedar Elms and a Spanish Oak in the backyard. Took the photo just a few minutes ago. Your site is absolutely amazing! Thanks for sharing! Julie Gracie Moseley
Your male Imperial Moth is a beautiful specimen.
Letter 4 – Male Imperial Moth
On Friday, July 29, we were visited by two male Imperial moths (I know this because of your loevly site!). Our friend Yi-Ren Tzeng got some nice pictures of one of them, which I am sending to you.
We are so very thrilled when people actually use our site to try to identify their critters before writing to us. We are so glad we were helpful.
Letter 5 – Male Imperial Moth
Oh my, what is it!?!?!
I came home earlier this evening and found "this thing" hanging out on the sliding screen door to my balcony. It kind of looks like a butterfly but it doesn’t to have any antennas. I live in Germantown, MD which is approx. 40 miles north of Washington, DC. My balcony faces a small wooded area. Can you tell me what this is that was visiting? Thanks for your assistance!
This is a male Imperial Moth. The female has more yellow and less reddish-purple on the forewings. He does have feathery antennae. They are hidden from view. The Imperial Moth, Eacles imperialis, is one of the Saturnid or Giant Silkworm Moths that do not feed as adults.
Letter 6 – Male Imperial Moth
Do you know what moth this is
I live on the north shore of lake huron and I found this moth. I cant seem to identify this moth can you help me out. Thanks
This is a male Imperial Moth. The female has more yellow on her wings.
Letter 7 – Male Imperial Moth
What species does this Moth belong to? Definately one of the bigger ones to drop by my porch here in north central Florida. Love your website! Thanks!
Judging by the greater amount of purple in the wings, this is a male Imperial Moth. The females are more yellow.
Letter 8 – Male Imperial Moth
Location: Richmond Hill (Savanah) Georgia
September 16, 2010 2:48 am
This moth I found is huge and furry. Living in the woods and near a bird sanctuary I see many different creatures of many shapes and sizes but this one was simply amazing. Please let me know what type of moth this may be. It has been on the same leaf for 3 days now and I would love to know what type it is! In the attached photos I tried to get some what of a measure to display how huge this thing is and in the second one you are able to relatively see it and it’s size from a distance located on the left bottom half of this crape myrtle tree. Check it out!
This is a male Imperial Moth. Are you sure that the shrub it is on isn’t in fact a Camellia rather than a Crape Myrtle?
Letter 9 – Male Imperial Moth
Location: Martha’sVineyard, MA
July 25, 2011 7:22 am
Never saw this big moth around before.
Curious what it might be.
This stunning creature is a male Imperial Moth. The female has more yellow wings than the male.
Letter 10 – Male Imperial Moth
Location: Jacksonville Florida
October 13, 2012 11:25 pm
This photo was snapped by our daughter, avid bug watchers here, never seen these, so pretty, hope it’s not some invasive crop destroyer?!?
Thank you for your time!
Signature: Thomas & Jamie
Dear Thomas & Jamie,
This is a gorgeous male Imperial Moth, Eacles imperialis. Females of the species have more yellow on the wings and males have more purple markings, though the highly variable markings range in color from “pinkish, orangish, or purplish-brown” according to BugGuide. They are not considered to be crop destroyers. According to BugGuide, the eating habits are described as: “Larvae feed on leaves of Bald Cypress, basswood, birch, cedar, elm, hickory, Honeylocust, maple, oak, pine, Sassafras (Sassafras albidum), Sweetgum (Liquidambar styraciflua), sycamore, walnut.
Adults do not feed.”
Letter 11 – Male Imperial Moth
Subject: Imperial Moth in North Carolina
Location: Clayton NC
June 21, 2013 5:17 am
Greetings! I saw this moth outside of work in Clayton NC (south of Raleigh) yesterday. I looked it up randomly and was surpirsed to see a web page that described it’s range as being in Canada – is that right? I never would have seen it against the brick if I hadn’t bent over to pick something up I had dropped & it’s wings fluttered in the wind. It was every bit as large as most Luna Moths I’ve seen.
Love your site!
Signature: George & Gracie’s Mom
Hi George and Gracie’s Mom,
Thanks for sending in this wonderful image of a male Imperial Moth. From what we have read, there are two or three subspecies in the U.S. According to the Butterflies and Moths of North America website: “Range: Maine west to eastern Nebraska, south to the Florida Keys and central Texas. Subspecies pini occurs across the northern Great Lakes basin and the northern third of Michigan’s Lower Peninsula” and “Subspecies pini feeds only on conifers.” That refers to the caterpillars because adults do not feed.
Letter 12 – Male Imperial Moth
Subject: Imperial Moth
Location: Pinehurst, NC
August 21, 2014 11:31 am
This moth has been on my bathroom mirror for 2 days. Why is it not moving?!?!
According to BugGuide, Imperial Moths have: “wings yellow, variably spotted and shaded with pinkish, orangish, or purplish-brown; male more heavily marked than female, especially in the south.” The male Imperial Moth in this image from BugGuide is colored and marked almost exactly like your individual.
We are going to speculate on your questions.
1. The light attracted your male Imperial Moth.
2. Like all Giant Silkmoths in the family Saturniidae, Imperial moths live long enough to mate, and in the case of the female, to lay eggs.
3. Flying when you are a Giant Silkmoth takes significant energy, and adults do not feed, needing to store fat and energy during the caterpillar stage.
4. We believe this male Imperial Moth was attracted to your light, and he is resting because he cannot sense a ready female nearby.
5. Male Giant Silkmoths have well developed antennae that can sense a female’s pheromones from a mile away.
6. If you allow him to rest, and he senses a female before he is ready to die, this male Imperial Moth will fly off into the night.
Letter 13 – Male Imperial Moth
Subject: Huge moth
Geographic location of the bug: Pollocksville, NC
Time: 03:52 PM EDT
Your letter to the bugman: Hello,
Wondering what type of moth this is. It is huge. Id say almost 4 inches across. Also its been sitting in same place all day. Is it possibly dying? Thank you so much.
How you want your letter signed: Sincerely, Dawn
This is a male Imperial Moth. The female Imperial Moth is lighter in color. Adult Giant Silkmoths like the Imperial Moth do not feed as adults and they live to mate. Flying takes energy. The male flies in search of a mate. If this male Imperial Moth does not sense a female through her pheromones, he may rest until he senses a nearby female.
Very interesting! Thank you so much.
Letter 14 – Male Imperial Moth rescued from Birds
Subject: yellow moth
Location: martinsville indiana
July 24, 2017 6:05 am
i found this moth outside the birds were trying to kill it i put in my flowers to try to save it im in indiana is this from here never seen one before
Signature: mrs williams
Dear Mrs. Williams,
You rescued a male Imperial Moth from the birds, and for that reason, we are tagging your submission with the Bug Humanitarian Award. According to BugGuide: “wings yellow, variably spotted and shaded with pinkish, orangish, or purplish-brown; male more heavily marked than female, especially in the south.” You can better understand that description by viewing a mating pair of Imperial Moths with the male in the lower position.
Ty for info and the award its doing good where I put him hopefully he makes it