Exploring the World of the IO Moth: A Detailed Guide

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The Io Moth is a fascinating species of moth that inhabits various parts of North America. Known for its large, striking eyespots on its hindwings, these moths attract the attention of both nature enthusiasts and curious observers alike. Males and females display distinctive color patterns, with males being generally yellowish and females showcasing brown, rusty red, or purplish tones on their forewings source.

Io Moths play an important role in our ecosystem, often serving as a food source for birds, bats, and other animals. Adding to their captivating appearance, Io Moths reveal their vibrant eyespots when they feel threatened, potentially scaring away predators source.

Some intriguing features of the Io Moth include:

  • Large eyespots on hindwings
  • Distinct color variations between males and females
  • Ability to scare away predators using their eyespots

Io Moth Basics

Scientific Name and Classification

The Io Moth (Automeris io) belongs to the order Lepidoptera and the family Saturniidae. It is a type of butterfly and has a close relationship with the Peacock Moth.

Physical Characteristics

Io Moths are sexually dimorphic. Here are the key features of both sexes:

  • Males: Generally yellowish wings
  • Females: More brown, rusty red, or purplish wings

The adult Io Moth has a wingspan of approximately 4 to 5 inches. One distinct feature is the large eyespots located in the middle of their hindwings. The caterpillar stage of the Io Moth also boasts unique features:

  • Spines capable of inflicting painful stings
  • Varying colors, such as green, orange, pink, red, and yellow on the body

Habitat and Range

Io Moths are found in North America, predominantly in areas with the following host plants:

  • Willow
  • Maple
  • Oak
  • Cherry
  • Pear

Their range stretches from the southern parts of Canada to Mexico and Florida. They primarily reside in deciduous forests.

Comparison Table: Io Moth vs Peacock Moth

Feature Io Moth Peacock Moth
Family Saturniidae Saturniidae
Order Lepidoptera Lepidoptera
Size 4 to 5-inch wingspan Larger than Io Moths
Eyespots Prominent on hindwings Less prominent

Morphology and Behavior

Male and Female IO Moths

Io moths are a type of moth found in forests and habitats with deciduous trees in the United States. Their forewing color differs between the sexes: males are generally yellowish, while females are more brown, rusty red, or purplish. Both male and female io moths have a distinctive large, prominent, blue and black eyespot on each hindwing.

Male Female
Forewing color Yellowish Brown, rusty red, or purplish
Eyespots Blue and black Blue and black

Larval Stage and Instars

Io moth caterpillars are green in color and have a silk-like texture. They go through multiple developmental stages, called instars, before transforming into an adult moth. The larvae feed mainly on the leaves of deciduous trees.

  • Green in color
  • Silk-like texture
  • Feed on deciduous trees

Adult IO Moths

Adult io moths are nocturnal creatures, meaning they are most active during night hours. They have a relatively short lifespan and do not eat during their adult stage. The adult moths’ primary focus is to mate and lay eggs.

  • Nocturnal
  • Short lifespan
  • Do not eat as adults

While io moth caterpillars are known to have a painful sting if touched, adult io moths pose no harm to humans. These fascinating creatures contribute to the rich biodiversity within their habitats and are an interesting subject of study for both scientists and nature enthusiasts.

Reproduction and Life Cycle

Mating and Eggs

Io moths typically mate at night, and after mating, females lay their eggs on host plants. Some common host plants where eggs can be found include:

  • Oak
  • Cherry
  • Pear
  • Elm
  • Sassafras
  • Coral bean
  • Salix (willows)

Eggs are often laid in clusters and hatch within a week or two, depending on the temperature.

Food and Host Plants

Io moth larvae are not picky eaters and can feed on a variety of trees, grasses, and shrubs. They are commonly found on plants like:

  • Oak
  • Cherry
  • Pear
  • Elm
  • Sassafras
  • Coral bean
  • Salix (willows)

Larvae eat their way through the plant leaves, growing in size and shedding their skin through multiple development stages, known as instars. During their growth, the larvae develop a distinctive white stripe along their body.

Pupa and Cocoon

Once io moth larvae have reached their final instar, they look for a suitable place to pupate, usually on branches or under leaves. Here they spin a silk cocoon to protect themselves while they transform into adult moths. The pupal stage lasts for around two weeks, after which adult io moths emerge from their cocoons.

Adult io moths have distinctive yellow forewings in males, while females have more brown, rusty red, or purplish coloration. The hindwings of both sexes have a large, blue and black eyespot, which they display to deter predators.

Io moths are native to North America and can be found from Georgia to southern Canada, making them adaptable to various ecosystems. In their adult form, io moths have a relatively short life span, focusing primarily on reproduction before passing away.

Defense Mechanisms

Stinging Spines

The IO Moth has a unique feature to ward off predators: stinging spines. These spines are:

  • Urticating
  • Painful
  • Venomous

These stinging spines serve as a deterrent for predators, causing a painful sting when they come into contact with them. The venom in the spines can cause discomfort, making predators less likely to attack.

False Eyespots

Another defense mechanism employed by the IO Moth is its false eyespots:

  • Located on the hindwings
  • Vibrant orange color
  • Resemble large eyes

These eyespots work by startling potential predators, making them think they are facing a larger, more dangerous creature. By displaying their brightly-colored hindwings, the IO Moth can effectively scare away threats.

Defense Mechanism Purpose Characteristics
Stinging Spines Deter predators Urticating, painful, venomous
False Eyespots Startle potential threats Located on hindwings, vibrant orange color, mimic eyes

Human Interactions and Connection

Greek Mythology and Names

The Io Moth, known scientifically as Automeris io, is named after the Greek goddess Io. The moth’s prominent eyespots on its hindwings are believed to resemble the eyes of Io, who is a character in Greek mythology. Some common names associated with the Io Moth include:

  • Peacock Moth
  • Yellow Emperor Moth
  • Adult Io Moth

University of Florida Research

Researchers at the University of Florida have been studying the Io Moth. Some key findings include:

  • Io Moths are polyphagous, meaning they feed on a variety of plants
  • They do not eat as adults, instead relying on stored nutrients from their larval stage
  • Common habitats: grasses, shrubs, and various types of plants

Endangered Status and Conservation

The Io Moth, while not currently endangered, is experiencing a decline in population due to habitat loss and other factors. Conservation efforts can focus on:

  • Protecting and preserving their natural habitats
  • Educating communities about the importance of the Io Moth and other pollinators
Characteristic Io Moth
Scientific name Automeris io
Greek connection Goddess Io
Primary food sources Various plants (polyphagous)
Adult feeding behavior Does not eat
Common habitats Grasses, shrubs, plants
Conservation strategies Habitat protection, education

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 – Saturniid Caterpillar from Costa Rica: Automeris phrynon

Subject:  Stinging Catapillar
Geographic location of the bug:  Palo Verde National Park, Costa Rica
Date: 08/06/2018
Time: 06:22 PM EDT
Your letter to the bugman:  I took this photo in Palo Verde but I was once stung by the same type in Barra Honda National Park. This is a dry lowland Karst topography but I have seen this or a similar caterpillar at my home at 1600m altitude in Heredia, Costa Rica. Can you Identify it and the type of moth it becomes? Thank You
How you want your letter signed:  Richard Tandlich

Caterpillar of Automeris phrynon

Dear Richard,
This is a positively gorgeous image of a very beautiful caterpillar in the genus
Automeris.  We believe that based on images posted to the World’s Largest Saturniidae Site that it is Automeris phrynon, and the site states that the caterpillars have urticating or stinging spines and that the:  “Body spines are quite long and almost appear to be ‘back-combed’ with the tips of the spines slanted toward the head.”  The adult moth is pictured on Tradebit and on Saturniidae Universe.  We can contact Bill Oehlke to see if he can verify its identity, and he might request permission to post your image to his site as well.  Would you grant permission?

Bill Oehlke confirms:
Very nice photo,
I agree that it appears to be phrynon. Thanks for requesting permission to post. Let me know how that goes.

Dear Daniel,
Thanks for your reply, compliment and info. You have my permission to reprint this photo since it has already been exhibited and seen by the public. Believe it or not, it was show at the SEVENTH INTERNATIONAL BIENNIAL OF CONTEMPORARY TEXTILE ART, in Montevideo, Uruguay. My wife is a textile artist and since she was doing all the translation work for this big exhibit she talked me into submitting to the photography section something that was “textile”. So I thought “hairy caterpillars” or spider web.  I’m not a pro photographer but I do love taking photos of things that don’t run away very fast. Our world here in Costa Rica is full of bugs, and bites and stings are part of life. Every so often I see something incredible either at home or on a hike and just have to capture it.
Richard Tandlich

Letter 2 – Stinging Caterpillar from Uruguay is Leucanella viridescens viridior

Subject: Pretty (poisonous?) caterpillar
Location: La Barra, Uruguay
March 7, 2013 2:35 pm
I encountered one of these during my recent trip to Uruguay and was told by the locals to stay away since it’s poisonous. The bright green/yellow color would definitely imply that it doesn’t want me to get too close. Any idea what it is?
Signature: Alex

Automeris Caterpillar
Leucanella viridescens viridior Caterpillar

Dear Alex,
We are nearly certain your caterpillar is a Giant Silkworm Caterpillar in the genus
Automeris, which includes many species of stinging caterpillars including the Caterpillar of the North American Io MothWe will check with Bill Oehlke to see if he can provide a species identification.  We often hear that locals have superstitions about perfectly harmless species being dangerous, including the Black Witch and the Lanternfly or Machaca, but in this case, the locals are right.

Bill Oehlke provides a correction:  Leucanella viridescens viridior
Hi Daniel,
It is Leucanella viridescens viridior, and they can give a nasty sting.
Bill Oehlke

Hi Daniel,
Thanks very much! Glad I didn’t touch it. 🙂

Ed. Note:  Bill Oehlke notes that it is the “Same subfamily Hemileucinae” as Automeris, hence our initial confusion.

Letter 3 – Male Io Moth

Moth ID
Dear “Bugman”,
Can you help with the ID of this nicely scary-“eyed” moth? We live in rural SE lower Michigan, about 30 miles west of Ann Arbor. Thanks,
Judy Gray

Hi Judy,
Many Sphinx Moths and Saturnid Moths, including your male Io Moth, have eyespots on the underwings that startle predators.

Letter 4 – Male Io Moth

Identification on moth
Good morning
I was hoping you can help me again on an ID. Thanks much

Hi Lorri
We wish you had provided a location for your male Io Moth.

Letter 5 – Male Io Moth

unknown moth
We found this moth this morning and when we released it outside, it landed on a tree and took this defensive stance. Can you please identify it for us? Thank you. Please reply to lmdavis@swmail.sw.org aSAP. Thanks again.

Hi Linda,
Your moth is a male Io Moth, Automeris io, one of the Saturnid Moths. Female Io Moths have brown forewings rather than yellow.

Letter 6 – Male Io Moth

Io Moth
Dear Bugman,
I found this beautiful Io Moth this afternoon in SW Florida. Absolutely gorgeous and cute as could be with his forelegs covering his eyes. I just had to share him with you. Thanks for all the great information. Your website is the best! Regards,

Hi Nik,
Thanks for the compliment, and thanks for sending us your photo of a beautiful male Io Moth.

Letter 7 – Male Io Moth

Beautiful Moth
Location:  Sarasota, FL
August 3, 2010 8:43 pm
Saw this moth outside of my office one day, it was yellowish and fairly big. it looked like it had color under it’s wings so I nudged it (very lightly I promise) to see the pattern under the wing. I was not disappointed as it had two very large faux eyes and bright red, yellow and orange coloring. Just hoping for an ID. Thanks a lot guys. Love the site by the way, found it Stumbling one day and I’ve been addicted since.

Male Io Moth

Hi Tim,
Thanks for the compliment.  Your moth is a male Io Moth.  The female is slightly larger and has brown upper wings.  The eyespots are very effective in dissuading predators like birds.  When the bird nudges the moth and the eyespots are revealed, what was once thought correctly to be a toothsome meal is mistaken for a large threat.  Interestingly, the Io Moth is one of the smaller North American Giant Silkmoths.

Letter 8 – Male Io Moth Illustrates protective Mimicry

Subject: large moth, approx. 2 inch wing span
Location: Northeast Pennsylvania
June 25, 2016 7:00 pm
found this on our slider, my husband knocked it off and it revealed inside wings..very pretty. We live in Effort, PA, Monroe County and it is summer time..June 25, 2016. Thinking it might be an Imperial moth, would appreciate further identification. After it was still, not moving, on the deck for a while, it moved to the bottom of the slider, then it’s wings started fluttering and then it took off.
Signature: Christine

Male Io Moth
Male Io Moth

Dear Christine,
This is a male Io Moth and your images nicely illustrate its protective mimicry.  Many Giant Silkmoths in the family Saturniidae, including your Io Moth, and some Sphinx Moths in the family Sphingidae have evolved an excellent survival strategy.  Markings on the underwings resemble eyespots and are known as ocelli.  When the moth is resting, the upper wings cover the underwings.  When disturbed, the moth reveals its underwings, flashing its eyes, potentially startling a predator like a bird into thinking it has awakened a sleeping giant.  Io Moths have also evolved to exhibit sexual dimorphism, meaning the two sexes have obvious visible differences.  Female Io Moths have brown upper wings.

Male Io Moth
Male Io Moth

Thank you very much for the information Daniel!

Letter 9 – Male Io Moth and Oakworm Moth

Subject: moth id
Location: middle tennessee
June 27, 2017 1:48 pm
found these on my porch. thought they were interesting. would like to know what they are. I have searched, but can’t find exact matches.
Signature: sequoia

Male Io Moth

Dear Sequoia,
Both of your moths are in the Giant Silkmoth Family Saturniidae.  The larger, yellow individual is a male Io Moth and if disturbed, he will display impressive eyespots on his underwings.  The smaller orange individual is an Oakworm Moth in the genus

Oakworm Moth

Letter 10 – Moth from Ecuador: Automeris argentifera

Subject: Ecuador cloud forest bugs
Location: mindo, ecuador
March 15, 2015 8:39 am
Both of these were found on the same morning in my house.. Any clues as to ID?
Signature: PB

Possibly Automeris abdomiorientalis
Possibly Automeris argentifera

Dear PB,
We are splitting your two requests apart so they can be better archived on our site.  We believe your moth may be
Automeris abdomiorientalis, and we are going to check with Bill Oehlke to get his opinion.  There are not many images of this species online, but you can compare your individual to the images posted on BOLD Systems Taxonomy.

Bill Oehlke Responds
Hi Daniel,
It is Automeris banus argentifera which has now been given full species status as Automeris argentifera.
Very nice image. Can you get permission for me to use image??

Letter 11 – Pre-pupal Great Peacock Moth Caterpillar from Portugal

Subject: Giant blue spiked Caterpillar
Location: Central Portugal
July 9, 2017 4:59 am
I found this big guy in front of my house,
The Caterpillar is about 10cm long, and has tiny hairs on top of blue bumps that are on his green/brown body.
I found him on a hot day at the beginning of summer, it were about 38°C outside, so I carefully took him to a shadow and took these pictures.
I live in central Portugal.
Signature: Karl

Prepupal Great Peacock Moth Caterpillar

Dear Karl,
Many caterpillars change color just before pupation, and this prepupal Great Peacock Moth,
Saturnia pyri, is no exception.  It began life as a green caterpillar and now that it is ready to spin a cocoon and pupate, it has changed to an orange color.  Here is an Alamy image that depicts a prepupal Great Peacock Moth caterpillar.  Alamy also has a nice image depicting the entire life cycle of the Great Peacock Moth.  The green coloration is depicted on UK Moths where it states:  “Europe’s largest moth, although not British, has been found on one occasion, in Hampshire in 1984. However, being such a spectacular species, it is a favourite amongst livestock breeders, and is unlikely to occur here in the wild.  Abroad, the distribution ranges from southern Europe through Africa and the Middle East.  The adults fly from April to June and are easily attracted to light.   The impressive caterpillars feed on the foliage of a range of foodplants, primarily fruit trees.”  Saturniidae of the Western Palaearctic has a nice comprehensive description of the Great Peacock Moth that includes this fascinating bit of information:  “Larger larvae are capable of ‘chirping’. These ‘chirps’ are broadband, with dominant peaks ranging between the sonic (3.7 kHz) and ultrasonic (55.1 kHz) and are generated by a rapid succession of mandibular ‘tooth strikes’. Chirp trains are induced by simulated predator attacks and precede or accompany the secretion of a defensive chemical from integumental bristles, supporting the hypothesis that these sounds function in acoustic aposematism. It has been proposed that these caterpillars generate multimodal warning signals (visual, chemical, and acoustic) to target the dominant sensory modalities of different predators, including birds, bats, and invertebrates (Bura, Fleming & Yack, 2009).”  Finally,  this Portuguese blog Natureza em Directo Borboletas has some nice images of the adult Great Peacock Moth.

Prepupal Great Peacock Moth Caterpillar

Letter 12 – Probably Automeris species

caterpillar 3
I’ve sent you this photo a few times, and I was just wondering if you’ve been able to find out what sort of caterpillar this is and what the butterfly would have looked like had my cocoon hatched. Some parasite got the better of him before he could complete the cycle. Thank you
Costa Rica

Hi Jordan,
This might be an Automeris species.

Letter 13 – Unknown Caterpillar: Automeris species

I hope you can help me…I found this caterpillar on my back porch in Prescott AZ. I am about a mile in altitude in the “high desert west”. I think it fell from some trees with that green material in the picture. I can’t figure out what it is. I am guessing it would sting me. Thank You,

Hi Craig,
This is some species of caterpillar in the genus Automeris. These are giant silkmoths. There are several possible species in Arizona, but none seem to match exactly. They include Randa’s eyed silkmoth or Automeris randa, and Cecrops eyed silkmoth or Automeris cecrops. A nearly identical image is posted to BugGuide with the possible identification being Automeris boudinotiana. Moths in the genus Automeris are known as the Eyed Silkmoths and some species have very localized populations. Automeris caterpillars do have stinging spines.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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2 Comments. Leave new

  • ‘Eyespot’ can either refer to the primitive invertebrate eyes found on many insects, or to the eye-like markings used for mimicry. ‘Ocelli’ (sing. ocellus) on the other hand, refers specifically to the primitive insect eye, not to the eyes used for mimicry on some insects. It is an easy mistake to make.

    • We are going to disagree with your take on the etymology. We are basing our use of the term Ocellus from the BugGuide definition where it states, as an alternate to the simple eye you mention: “An eye-like spot of color, consisting of annuli of different colors, enclosing a central spot or pupil, as present on the wings of some lepidoptera. Photos of the eye-spot type of ocelli.” The term Eyespot, on the other hand, does NOT refer to the simple eyes. According to our understanding, Ocellus can be either but Eyespot refers only to the marking that does not have vision.


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