Ceanothus Silkmoth: Essential Facts and Fascinating Insights

The Ceanothus silkmoth, scientifically known as Hyalophora euryalus, is a fascinating species.

These moths are native to North America and can be predominantly found in the western regions of the United States and Canada, where they contribute to the ecosystem as important pollinators.

The unique appearance of the Ceanothus silkmoth and its lifecycle makes it an interesting subject for enthusiasts and researchers alike.

One of the most striking features of the Ceanothus silkmoth is its large, vibrant wings with intricate patterns.

The combination of beautiful shades of brown and white with prominent eye spots gives this moth a captivating aesthetic.

It is not only the adult moths that exhibit fascinating characteristics; the caterpillars of these moths are also quite intriguing with their vibrant colors and hair-like structures.

In this article, we delve into the world of the Ceanothus silkmoth, covering interesting facts and information that make this species a must-know for anyone passionate about the natural world.

Ceanothus Silkmoth Overview

Classification and Appearance

The Ceanothus silkmoth (Hyalophora euryalus) belongs to the Lepidoptera order. This species is known for its striking appearance, with features such as:

• Large size, typically with a wingspan of over 4 inches
• Bold patterns, including a distinct white band across its wings
• Eyespots on the wings, which may deter predators

Geographical Range and Habitat

The geographical range of the Ceanothus silkmoth covers parts of:

• North America
• British Columbia
• California
• Canada
• Mexico

It is native to North America and can be found between British Columbia to Baja California Sur, covering regions in the United States and Canada.

It inhabits a variety of environments including coastal areas, chaparral, and conifer forests.

Life Cycle and Behavior

Mating and Reproduction

The Ceanothus silkmoth (Hyalophora euryalus) exhibits a fascinating mating process.

Male silkmoths can detect female pheromones from miles away, and they use their large wingspan (up to 5 inches) to locate their mates.

After successful mating, the female lays her eggs on host plants.

Eggs

• Typically laid in clusters
• Hatched within two weeks

Ceanothus silkmoth eggs are laid in clusters on a host plant, with hatching occurring within two weeks.

The eggs take on a round, flat shape and vary in color, from pale yellow to light green.

Larva

• Vivid coloration
• Feeding on host plants

The caterpillars boast a unique appearance, possessing bright coloration and prominent eyespots to deter potential predators.

During this stage, they primarily focus on eating and growing. Caterpillars can commonly be found feeding on their host plants, such as Ceanothus, for sustenance.

Cocoons

The final stage in the Ceanothus silkmoth lifecycle is the cocoon stage. Caterpillars transform into a pupa and encase themselves in silk.

• Pupa undergoes metamorphosis
• Silk cocoon provides protection
• Emergence as adult moths

While encased in the cocoon, the pupa undergoes metamorphosis and becomes an adult silkmoth.

The cocoon serves as protection against predators and weather during this vulnerable time. After completing the metamorphosis, the adult moth emerges, and the cycle begins anew.

Host Plants and Food Sources

Common Host Plants

Ceanothus silkmoth larvae are commonly associated with a variety of host plants. These plants provide a habitat and food source for the caterpillars. Some of the common host plants include:

• Ceanothus species (also known as Wild Lilac)
• Arctostaphylos (Manzanita)
• Alnus (Alder)
• Ribes (Gooseberry and Currant)
• Salix (Willow)
• Betula (Birch)
• Prunus (Cherry)
• Acer (Maple)
• Amelanchier (Serviceberry)

These plants are often found in chaparral and coastal areas, providing essential resources for the Ceanothus silkmoth.

Food Resources for Larvae

The Ceanothus silkmoth larvae depend on their host plants for sustenance. A few specific examples of host plants that are commonly consumed by the larvae include:

• Ceanothus thyrsiflorus ¹
• Arctostaphylos manzanita
• Alnus rubra (Red Alder)
• Ribes sanguineum (Flowering Currant)
• Pseudotsuga menziesii (Douglas Fir)
• Arbutus menziesii (Madrone)
• Salix lasiolepis (Arroyo Willow)
• Rhamnus californica (California Buckthorn)

Here’s a comparison table of some common host plant features:

Host Plant	Plant Type	Growth Habit	Native Range
Ceanothus	Shrub	Upright	North America
Arctostaphylos	Shrub	Upright	North America
Alnus	Tree	Upright	North America, Europe
Ribes	Shrub	Upright	North America, Europe
Salix	Tree/Shrub	Upright	Worldwide

The availability of these host plants in the larvae’s habitat enhances their survival and contributes to the continuity of Ceanothus silkmoth populations.

Conservation and Human Interaction

Migratory Patterns and Concentrations

The Ceanothus silkmoth (Hyalophora euryalus), belonging to the kingdom Animalia and class Insecta, is an organism mainly found in North America.

Not known for long migratory patterns, this silkmoth primarily resides in environments rich in food resources like coniferous forests and meadows.

Some key facts about their habitat:

• Prefers coniferous forests and meadows
• Found mainly in North America

Interactions with Humans

As members of the genus Hyalophora, Ceanothus silkmoths are not directly harmful to humans. People often encounter these moths incidentally while enjoying outdoor activities or gardening.

In fact, their presence can be an indicator of a flourishing ecosystem. 

Female silkmoths release pheromones to attract males for mating. A downside to this is their vulnerability to artificial light, as it can interfere with mating activities and reduce their population.

Despite the challenges they face, the Ceanothus silkmoth population is not yet at risk. Conservation efforts should focus on preserving their natural habitats and minimizing light pollution.

Additional Information

Weather Influences on Behavior

Ceanothus silkmoths, like other members of the Saturniidae family, may exhibit changes in behavior according to the weather.

For example, their activity often increases during warmer periods. Some known factors that can influence their behavior include:

• Temperature fluctuations
• Humidity changes
• Rainfall or precipitation events

Comparisons to Other Silkmoths

Ceanothus silkmoth shares some common features with other silkmoths such as Samia rubra and Columbia silkmoth.

However, there are also some noticeable differences. A comparison of their characteristics can be found in the table below:

Feature	Ceanothus Silkmoth	Samia Rubra	Columbia Silkmoth
Color	Purple, pink, and orange	Light brown and cream	Yellow and reddish-brown
Antennae	Comb antennae	Comb antennae	Comb antennae
Wing Shape	Big rounded wings	Rounded wings	Rounded wings
Wing Tip Eyespot	Pointed comma shape	Crescent-shaped eyespots	Prominent eyespots
Size	Large (4-5 inches)	Medium (3-4 inches)	Large (4-6 inches)

Key features of the Ceanothus silkmoth include:

• Comb antennae
• Huge body size
• Big rounded wings
• Unique pointed comma wing tip eyespot

Conclusion

In conclusion, the Ceanothus silkmoth, Hyalophora euryalus, stands out for its vibrant and intricate appearance, playing a vital role as a pollinator in North America.

With a lifecycle deeply intertwined with various host plants and a presence indicating a thriving ecosystem, this moth is a fascinating subject for nature enthusiasts.

Despite facing challenges like artificial light interference, it remains secure, highlighting the importance of conservation efforts and coexistence with this captivating species in our diverse North American landscapes.

Footnotes

1. Ceanothus thyrsiflorus – North Carolina Extension Gardener Plant Toolbox ↩

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 – Ceanothus Silk Moth

What is this Moth?
Thu, Mar 19, 2009 at 2:29 PM
this moth was hanging on the window screen of our house from about 7am when i first noticed it, and was there all day and disappeared sometime in the night after 11pm. it was almost 5 inches wide (as seen in the picture) and very rusty/red.

we live about an hours drive south of San Fransisco, California, and about a 30 minute drive from the beach. our house is in the Santa Cruz mountains, about 600ft elevation.

this is easily the biggest and most colorful moth I’ve seen (although I’m only 17 and havent seen much) and i would love to know what it is
Will Lawton
Redwood Forest, in the mountains, near the ocean

Dear Will,
Congratulations on your sighting of a Ceanothus Silk Moth, Hyalophora euryalus, one of the Giant Silk Moths.  It is wonderful that you included both and open winged and closed winged shot and also that your included a ruler. 

All of this will assist our West Coast readers who should begin sighting this moth now that spring is approaching.  According to BugGuide:  “adults fly from January to July, depending on altitude, latitude, and seasonal variation”  and  the species ranges from “British Columbia to western Montana, south through west coast states to Baja California.

In California, found mostly west of the Sierras. Habitat coastal areas, chaparral, intermontane valleys, conifer forests.”  The caterpillars feed on a variety of leaves including the California lilac or Ceanothus.  Adults do not feed.

Letter 2 – Ceanothus Silkmoth

Glover’s Silk Moth?
January 16, 2010
We are in the hills near Temecula and have willows, buckbrush, ceanothus on the property.
Thanks for any additional information.
Matt Stone
Temecula, CA 92592

Hi Matt,
Your visitor is a Ceanothus Silkmoth, Hyalophora euryalus, a California native that does not feed as an adult, but has a caterpillar that feeds on Ceanothus, or California lilac.  According to BugGuide, the larvae also feed on willow, so your property should be a natural habitat for the Ceanothus Silkmoth.

Letter 3 – Ceanothus Silkmoth

northern california moth, June 11
Location: menlo park, california
June 8, 2011 12:59 pm
What’s this bug, please?
Signature: friendly neighbors

Dear friendly neighbors,
We are trying to figure out how you spotted this Ceanothus Silkmoth three days after submitting your identification request.

lol.  you funny people. “Jun 11” meant “June 2011.” we saw it the morning of June 8th.
we are on the west side of the San Francisco Bay valley, just a couple blocks from the start of the foothills. The guest was next to our front door all day, and now we know it was a Ceanothus Silkmoth. Thanks!

Thanks for the clarification.  Exact dates can be very important in insect sightings especially when lifespans are short.  Ceanothus Silkmoths rarely live longer than a week.  They do not eat as adults and the male can sniff a females pheromones with his antennae from many miles away.  He is built for flying and she is built for laying eggs.

Letter 4 – Ceanothus Silkmoth subspecies Caterpillar

Subject: Beautiful caterpillar
Location: In between Fernan Saddle and Wolf Lodge Creek
July 5, 2015 10:58 am
Sooo….were out huckleberry picking on Independence Day and my daughter says “Dad, check out this cool caterpillar I found”. I walk over to her and to my amazement find the coolest Independence Day caterpillar ever! It’s got red spikes, blue spikes, and white dots and they look like fire works too!
Signature: Joe Hitz

Dear Joe,
Your images are spectacular.  While we are certain your caterpillar is a Giant Silkmoth Caterpillar in the genus Hyalophora, we are not certain if it will become a Ceanothus Silkmoth or a Columbia Silkmoth as both species have very similar looking caterpillars. 

We are leaning toward the Ceanothus Silkmoth Caterpillar, Hyalophora euryalus, and according to BugGuide:  “Larvae feed on a number of trees and shrubs, including Red Alder (Alnus rubra), birch, Antelope Bitterbrush (Purshia tridentata), buckthorn (Rhamnus), Buffaloberry (Sheperdia canadensis), Ceanothus species, cherry, gooseberry (Ribes), Hardhack (Spiraea douglasii), hazel, Madrone (Arbutus menziesii), manzanita (Arctostaphylos), Mountain Mahogany (Cercocarpus betuloides), Mountain Maple (Acer glabrum), rose, Saskatoon Serviceberry (Amelanchier alnifolia), willow (Salix), and occasionally Douglas-fir (Pseudotsuga menziesii).” 

According to BugGuide, the caterpillar:  “changes colors as it develops and molts; mid instars are the most brilliantly colored with nine pairs of dorsal yellow spines, the first three pairs with partial to complete black rings; a middorsal yellow spine on A8; two rows of lateral blue spines tipped with white along T1-A8; white-tipped blue spines also occur on the head, at the base of the true legs, and in the anal region; body ranges from green to whitish-green  later instars whitish-green with white spines.” 

You can see examples of both species on BugGuide, but your individual is more brightly colored than most of the images posted there.  We will try to contact Bill Oehlke to see if he can determine the species.

Bill Oehlke Responds
Daniel,
Idaho is a big state. It seems most like Hyalophora [euryalus] kasloensis. A more precise location would help.
There is also a hybrid zone in Idaho.
Very nice images. My first choice would have to be kasloensis, although this may only be third instar.
Bill

Thanks Bill.  the location is:  “In between Fernan Saddle and Wolf Lodge Creek”

Daniel,
Based on location it is Hyalophora euryalus, the ceanothus silkmoth.
Please see if I can get permission to post images. I suspect it is third instar.
Bill

Letter 5 – Ceanothus Silkmoth from British Columbia

Subject:  Furry moth
Geographic location of the bug:  Courtenay BC
Date: 05/02/2019
Time: 10:04 PM EDT
Your letter to the bugman:  Hey what kind of moth is this? Its big and furty with fern-like antenea?
How you want your letter signed:  Thank you

This is a Giant Silkmoth in the genus Hyalophora, and we are relatively certain that it is the Ceanothus Silkmoth because of the BugGuide description:  “discal spot on hindwing shaped like an elongated comma pointing toward outer margin, sometimes breaking PM line.”  We believe because of the bushy antennae that your individual is a male.

Letter 6 – Mystery: Possibly Issid Planthopper on Ceanothus

Rocket Bug
April 15, 2010
Photos are 2010-04-10
Three stages of the bug
Host plant is Ceanothus megacarpus
Santa Monica Mountains, CA
Bug oozes clear fluid
Bug length ~ .25 inch
Pinetar
Santa Monica Mountains, CA

Dear Pinetar,
This is a Planthopper in the superfamily Fulgoroidea, but we have not had much success identifying the species on BugGuide.  Your photos are quite wonderful and comprehensive.  They depict the winged adult as well as the nymphs, and the white individual is a newly metamorphosed adult.

We like when the host plant species is identified in the letter as that often helps in the identification, but in this case, our early attempts at species identification have drawn blanks.  We are going to try to find some experts who can assist in this identification, but we have additional questions. 

Is the host plant in a garden or is it growing wild?  We believe your individuals are in the family Issidae which is represented on BugGuide with this information:  “Issidae usually have shorter wings than Flatidae, and lack the warty surface on the forewings where they meet over the back. Issid nymphs have straight, bundled wax filaments projecting from the rear, not bushy as in flatid nymphs.“

Daniel
Thank you for your speedy and accurate reply. I am impressed.
Your ID as Issid Neaethus (photo 64951) looks darn close.
My darling Rocket Bugs are from the wilds of the Santa Monica Mountains – on the Old Boney Trail at ~1,800ft.
I have attached 3 more frames that might help.
304    –  rocket bug face-off
310    –  another close-up of our plant hopper
299    –  this frame has 2 interesting features
1 – 2 nymphs in an alternate phase, where the rocket exhaust is gone,   the abdomen is greatly swollen,   the eyes have darkened  and  the wings are enlarged and in permanent extension.  Perhaps it is about to enter metamorphosis

2 – note the clear fluid on a twigglet near the bottom of the frame – this is from the plant hoppers. It caused the ground to look like it had rained and is what made me stop and investigate the source.

At first I thought the ‘rain’ was coming directly from the ceanothus – and without thinking I tasted it – now my wife says I’m beginning to resemble a rocket bug –  I do have to admit that the little guys are starting to look darn right beautiful to me  – and maybe I am developing a hankering for that big-pod buckbrush – so what. She hopes I enter metamorphosis and fly away.

Oh well – it’s all for science – there has to be some sacrifice.
Thanks for your continued interest in this bug.
Let me know what you scare up.

Hi John,
Thanks so much for the follow up information.  We will link to Neaethus on BugGuide.  Many Aphids and Planhoppers exude honeydew which is sweet and sticky.

Letter 7 – Badly Battered Ceanothus Silkmoth

Ceanothus Silkmoth Comment
Location:  Anderson, CA
March 5, 2015
I just found one tonight (3-5-15) at our home in Anderson, CA didn’t know what it was for sure so I looked and this image came up, the one I found looks the exact same! Beautiful moth.
Ali

We wish you had sent in a photo as we have not posted a Ceanothus Silkmoth image recently.

This is the moth we found it was battered pretty bad but still flying.

Dear Ali,
Thanks for sending us your image of a battered Ceanothus Silkmoth.  Adults only live a few days, long enough to mate and lay eggs.  They do not even feed as adults as they do not have working mouthparts.  Adult life is dangerous for a Silkmoth. 

They store fat while a caterpillar to get them through the adult stage, and they are an excellent food source for birds and other predators.  Hopefully your individual mated and was able to pass on its genes to a new generation.

Letter 8 – better photo of same Ceanothus Silkmoth from the photographer

Moth like wings spiny red legs
January 14, 2010
Hi,
Found this bug on the outside of our house. It is about the size of the palm of your hand and has wings that look like a moth’s, but spiny crab-like legs. It didn’t move from the same spot for 3 days, and just today was gone. Any ideas? Thanks!
Not a big bug fan
San Diego, CA

Dear Not a big bug fan,
Interestingly, your friend L sent us this exact photo yesterday, but it was a lower resolution and we were lamenting to ourselves that the resolution was so poor.  L will probably be disappointed to find out you already know the answer.

We didn’t tell L the scientific name is Hyalophora euryalus, or that the natural range is from Baja to Canada along the westernmost portion of North America. Here is what we wrote back to L a few minutes ago.

This is a Ceanothus Silkmoth.  With more Southern California Landscaping being mindful of drought tolerant plants, especially native vegetation, we expect to be getting more reports of sightings of Ceanothus Silkmoths each year. 

Your letter does not indicate if your friend lives near any natural open space, as this native moth, which does not feed as an adult and only lives for a few days, long enough to mate.  The Ceanothus Silkmoth develops from a large caterpillar that feed on the leaves of ceanothus, a plant sometimes marketed as California lilac. 

BugGuide reports California sightings from March through August, so this January appearance is uncharacteristically early, but it may also be a result of our unseasonal rains this past October.

Thank you!  You solved the mystery, you guys sure know your bugs :). Very interesting looking moth.

Letter 9 – Ceanothus Silk Moth

Spectacular Moth… But What is It?
Dear Bugman:
My family loves your site, especially since we move often and recently moved to southern California. My four young kids have discovered all sorts of new bugs here – and I was so grateful to have discovered a potato bug on your site – the first one my children brought me had me more worried than the scorpions and black widows we routinely encountered in AZ.

This morning, this lovely moth was relaxing in our front entry. My husband thought he was a polyhemus, but he has white swoosh-shaped markings on his wings where a polyhemus has golden eyes. He was easily 5 inches wingtip to wingtip, with the thick fringe antennae of a polyhemus, and a furry brown and white striped body, very furry legs. What the heck is he?

We’ve let him go in a backyard tree and hope he procreates and becomes a regular site. We live in De Luz, California, sandwiched between the coastal climate of North San Diego County and the dry wine country valleys of Temecula and are hoping that this lovely creature is a native and likely to be seen again.
Sarah Smith

Hi Sarah,
Thank you for the nice letter. We are very happy to post your photos of the Ceanothus Silk Moth, Hyalophora euryalus, one of the Saturnid Moths. This truly spectacular moth is native and the caterpillar feeds on the Ceanothus Tree, or California Lilac. The adults do not feed.

Letter 10 – Ceanothus Silk Moth

Ceanothus Silk Moth
Hello,
Just wanted to share the photo of the beautiful moth we found in my mom’s backyard on Sat. 5/20/06, the neighbor Dick decided to take a picture of it and he gave it to us. Isn’t it pretty.
Andrea Beutler
Santee, CA (San Diego)

Hi Andrea,
Not only is the moth beautiful, the photo is gorgeous. It is just the type of photo that appeals to our aesthetic, and if we do a calendar next year, we would love to use it.

Letter 11 – Ceanothus Silk Moth

Ok, just curious, it this a rare bug (it flew away already)
we live in the high desert in San Diego County
Joseph Rauh
Ranchita, CA

Hi Joseph,
The Ceanothus Silk Moth, Hyalophora euryalus, is not really rare, but few people are lucky enough to see the spectacular Saturnid Moth. They fly in the spring, are sometimes attracted to lights, and do not feed as adults. They live and fly solely to mate.

Letter 12 – Ceanothus Silk Moth

Ceanothus Silk Moth, Hyalophora euryalus, one of the Saturnid Moths
Ceanothus Silk Moth found North of Fort Bragg, California on the Pacific Ocean on 3/24/2006. This beautiful creature enthralled us, and stayed in this position all night and all day… Until the owner claimed her shoe. The bottom of the lower wings look like children holding hands and dancing! Thank you for your wonderful and educational site!
Anna Andrews

Hi Anna,
Thanks for sending us your wonderful image of a properly identified Ceanothus Silk Moth.

Letter 13 – Ceanothus Silk Moth

Ceanothus Silkmoth
Hello Bugman,
On April 26, 2007 at around 12:12 in northern San Diego, I caught this gorgeous Ceanothus Silkmoth Hylaphora Euryalus with a U.V light. Here are some photos, if you have the moment, maybe you can post them. Thanks
Rani Cohen

Hi Rani
Thank you for sending us your wonderful images of thie beautiful Ceanothus Silk Moth.

Letter 14 – Ceanothus Silk Moth

Moth identification help please!
Dear Bugman,
I found this beautiful moth on my front window this morning. We live in Foresthill, CA, which is in the foothills of the Sierra Nevada Mountains. The elevation is about 2500 feet. I would appreciate if you could identify this lovely species for me. Thank you very much.
John N.

Hi John,
This is a Ceanothus Silk Moth, Hyalophora euryalus. It gets its name from one of its food plants, the Ceanothus or California Lilac.

Letter 15 – Ceanothus Silk Moth

What is this moth called?
This was a visitor to our window a few days back. Its hard to tell from the picture, but it was huge. Can you please tell me what it is? Thanks,
Arlene Miller
Los Altos Hills, California

Hi Arlene,
This is a Ceanothus Silk Moth.

Letter 16 – Ceanothus Silk Moth

Not sure what this is
Hi – could you please assist me with what kind of moth this is? Thanks
Gloeta

Gloeta, Could you show this to your science colleagues who might be able to tell me what it is ? I came across this beautiful “thing” the other day and tried to get a clear picture. Thanks for your input.
Susan Williams, Principal
Lompoc Adult Education
Lompoc, CA

Hi Susan and Gloeta,
This beauty is a Ceanothus Silk Moth, Hyalophora euryalus.

Letter 17 – Ceanothus Silk Moth

Luna Moth???
could you tell me what this is ? seen one flying around and thought it might be the same kind as my cocoon. Hey I found this cocoon the other week and beleive it is a luna moth after visiting your website. It did have a little whole in the cocoon , so i decided to open it a little and see if the bugger was still alive , Sure he was . moves around once in abit.

The reason i am e-mailing you is because one of the moths on your site was found on oHio , which you had mentioned was pretty far north. Well i live in the Northern Panhandle of idaho , about 5 miles from canada and in 24 years of living here , i have never found something like this.

How long do they usually take to hatch ? going on two weeks now , but its been very cool outside and even inside. any info wold be greatly appreciated . Thank you

This is a Ceanothus Silk Moth, probably the same as your cocoon.

Letter 18 – Ceanothus Silk Moth

Cecropia Moth in San Francisco
I came across your site after finding a cecropia moth at my office near San Francisco and saw that you told someone previously that the one they found must have been an escapee.

After doing some research and verifying with entomologists at California Academy of Sciences, it was determined that the moth I found (as well as the one found by your previous poster) is a Hyalophora euryalus , or Ceanothus moth, common to the west coast of the US.

You reorted to Chris and Josephine that they only occur east of the Rockies.
Just thought I would clarify. I have attached a picture of the moth I have found.
Cheers,
Chris

Hi Chris,
We are in full agreement that your moth is a Ceanothus Silk Moth, Hyalophora euryalus, but we still believe the previous posting from San Francisco is a closely related Cecropia Moth. The red edges on the wing markings and striped body are visual cues that lead us in that direction.

We are not however entomologists. We are artists, and if an entomologist said the previous moth is a Ceanothus Silk Moth, we will defer, however, if you are basing this soley on the image that you have sent us without the entomologist reviewing the other image, then we cannot agree.

Letter 19 – Ceanothus Silk Moths Mating

giant moths 5/25/06
I discovered these moths mating this morning on my deck. I live in north eastern Washington (Deer Park). They are very large as that is a 4X4 post they are on. I would say at least 5 1/2 to 6 inch wing span. They were very beautiful, and strikingly large!! Like WOW!! So, What are they?

Here’s some pixs. The antennae were beautifully delicate. Notice how the tip of the right wing looks like the eye and nose of a snake or lizard!! These moths were in great shape and gone when I came home from work. I guess it was just a one night stand. Thanks for looking.
Rob.

Hi Rob,
Your moths are Ceanothus Silkmoths, Hyalophora euryalus, and they could well have had a one night stand. They can be distinguished from the Columbia Silk Moths, according to Bugguide, because the “discal spot on hindwing shaped like an elongated comma pointing toward outer margin …”. Adults do not eat, they live to mate. The female will lay eggs and die and her mate will probably die sooner.

Letter 20 – Ceanothus Silkmoth

2 pictures for you
We found this beautiful moth on our North Idaho ranch about 60 miles south of the Canadian boarder. In our 40 years here we have never seen anything like it. Is this a Columbia Silk Moth?
C

Hi C,
This is a close relative of the Columbia Silkmoth, the Ceanothus Silkmoth, Hyalophora euryalus. It is found in the western states.

Letter 21 – Ceanothus Silkmoth

Ceanothus Silk Moth, Hyalophora euryalus
Hello 🙂
I just recently started surfing your awesome webpage and thought I would send in a nice picture I got of a Ceanothus Silk Moth. This little guy was hanging out at a gas station in the Sacramento Valley, California in late June 2007.

I had just recently left to visit the college I am currently attending when I snapped this photo. 🙂 Moths are my favorite type of insect, so needless to say, he cheered me up quite a bit and cured me of some of my nervousness about leaving home. Hope you enjoy the photo! Sorry if it’s a little large!
Jenny

Hi Jenny,
Thanks so much for sending us your wonderful photo. Good luck at your new school.

Letter 22 – Ceanothus Silkmoth

What is this insect?
January 13, 2010
This bug (moth?) has been on the side of my friends house for a few days. She lives in San Diego County. It’s January.
She says the legs are crab like and it is about the size of her hand.
L
San Diego, California

Dear L,
This is a Ceanothus Silkmoth.  With more Southern California Landscaping being mindful of drought tolerant plants, especially native vegetation, we expect to be getting more reports of sightings of Ceanothus Silkmoths each year. 

Your letter does not indicate if your friend lives near any natural open space, as this native moth, which does not feed as an adult and only lives for a few days, long enough to mate.  The Ceanothus Silkmoth develops from a large caterpillar that feed on the leaves of ceanothus, a plant sometimes marketed as California lilac. 

BugGuide reports California sightings from March through August, so this January appearance is uncharacteristically early, but it may also be a result of our unseasonal rains this past October.

Letter 23 – Ceanothus Silkmoth

Ceanothus Silkmoth?
Location: Near Barona Indian Reservation, San Diego County
January 21, 2011 2:36 pm
We found this very cool looking creature perched outside our home’s front door in the early dawn yesterday morning. When we arrived home late evening, it was still in its same position. I thought it was a massive butterfly, while my boyfriend called it a pterodactyl. The wingspan must have been 6” – 8”! From pics on your site, I’m guessing it’s a ceanothus silkmoth?
Signature: Dana

Hi Dana,
We love hearing from people who have no idea what they have seen, yet they are able to identify the mystery creature on our site.  You are absolutely correct.  This is a Ceanothus Silkmoth.  It appears that your specimen is a male based on his feathery antennae.

Letter 24 – Ceanothus Silkmoth

what kind of moth?
Location: Silverado, California
February 1, 2011 12:07 am
Hi, my niece snapped this pretty moth today at her barn. Wondering what type of moth it is so we can further study it.
Signature: Sandy

Dear Sandy,
This lovely moth is a Ceanothus Silkmoth.  The caterpillars feed upon the leaves of the California Lilac or Ceanothus, and despite planting several of these pretty native shrubs in the garden, we have been unable to lure the Ceanothus Silkmoth to our Mt Washington, Los Angeles offices.

Letter 25 – Ceanothus Silkmoth

Moth identification
Location: Trinity National Forest, Trinity County, CA / May 30th / 2,500 ft elevation.
May 31, 2011 9:40 am
I looked through the large moth photos and did not see this particular guy. Some of the silk moths were close, but not spot on. It has about a 4.5 inch wing span. Any help would be appreciated.
Signature: K. Fisher

Dear K. Fisher,
Your lovely moth is a Ceanothus Silkmoth, Hyalophora euryalus.  The distinguishing feature of this species is the “discal spot on hindwing shaped like an elongated comma pointing toward outer margin” according to BugGuide.

Letter 26 – Ceanothus Silkmoth

Cecropia Moth
Location: Los Gatos, California
June 20, 2011 6:44 pm
Hi there,
I saw this beautiful moth in Los Gatos, California yesterday. After doing a little bit of research trying to identify the type of moth that I saw, I kept coming across information that the cecropia moth isn’t found in California. I was wondering what you thought of this or if I am correct in identifying this moth.
Signature: Gretchen

Dear Gretchen,
Unlike the Cecropia Moth, the closely related Ceanothus Silkmoth, Hyalophora euryalus, is indigenous to Southern California.

Letter 27 – Ceanothus Silkmoth

Hyalophora cecropia
Location: Mariposa, CA
March 30, 2012 7:04 pm
Hi bugman!
We found this beautiful silkmoth in our living room. I understand that this moth usually is found east of the Rockies. We are in Mariposa, CA. Thought you might enjoy this sighting.
Signature: Kristin

Dear Kristin,
Your identification is not correct, but the error is understandable.  You have identified your moth’s genus correctly, but you were visited by the Ceanothus Silkmoth, a relative of the Cecropia Moth that ranges along the west coast.  The bushy antennae identify this as a male.  You can get additional information on the Ceanothus Silkmoth on BugGuide.

Letter 28 – Ceanothus Silkmoth

Subject: HUGE Moth/Butterfly Thing
Location: Southern California (Glendora)
August 14, 2012 10:39 am
Dear ”bugman”,
I saw this thing outside of my house in March. I have NO idea what this thing is, but I’d love to know. I’ve been trying to google it but I can’t find it. I want to know the exact name of it 🙂
Thanks!
Signature: Curious Girl

Dear Curious Girl,
This is a male Ceanothus Silkmoth.  Thank you for including information that the sighting occurred in March since such appearances are generally very much tied to climate conditions like temperature and humidity.

Letter 29 – Ceanothus Silkmoth

Subject: winged-caterpillar-spider bug
Location: Alpine, CA
March 21, 2013 1:11 pm
I saw this bug on the ground outside my office on 3/20/13 in Alpine, CA. I have never seen anything like it. It looks like a combination of a spider, butterfly, and caterpillar. It seemed to be trying to walk and/or fly and seemed to be having trouble doing either. Is no longer there, so unsure what happened to it. Was quite large-body was about 1 inch, wings were maybe 2 inches.
Signature: Jennifer

Hi Jennifer,
This is a Ceanothus Silkmoth, Hyalophora euryalus, and this is not the first time that we have received a letter requesting the identification of a large moth that was compared in appearance to a caterpillar.  You can find more information on the Ceanothus Silkmoth on BugGuide. 

Letter 30 – Ceanothus Silkmoth

Subject: Is this Callosamia angulifera
Location: El Granada, California
May 29, 2015 4:59 pm
This big beauty was hanging on the wall outside my apartment, in El Granada (Half Moon Bay) California. Is this species native to the coastal SF Bay Area?
Signature: Spencer

Dear Spencer,
Your beautiful moth is a Ceanothus Silkmoth, Hyalophora euryalus, and judging by the antennae, he is a male.  It is native to your area.  You can find additional information on BugGuide.

Letter 31 – Ceanothus Silkmoth

Subject: moth
Location: southern oregon
April 27, 2016 11:32 pm
Dear Burman,
I see this moth all the time and would love to know what it is. I thought it was a polphemus but the eyes are placed wrong…
Thank you
Signature: Jessica Hulsey

Dear Jessica,
This gorgeous moth is a Ceanothus Silkmoth, a west coast species related to the Polyphemus Moth.

Letter 32 – Ceanothus Silkmoth

Subject: Large moth
Location: Corona, California
March 11, 2017 4:57 pm
We found a large moth (5″ wing-span) fluttering around the other night in our backyard, and was wondering what kind it might be. It landed and stayed in the same spot for over a day, until unfortunately it died.
Trying to look it up, to me it looked a lot like the Glover Silkmoth, but also looked kind of like a Cecropia. However, I couldn’t find where either of those moths live in Southern California where we’re located.
I know absolutely nothing about moths and hoped you could help.
Thank you!
Signature: MC

Dear MC,
This female Ceanothus Silkmoth, Hyalophora euryalus euryalus, is in the same genus as the Glover Silkmoth, hence the similarity in their appearances.  According to BugGuide, the range is:  “British Columbia, Canada south through the west coast states of the USA into Baja California (c. Mexico).  In California, found mostly west of the Sierras.”   Like other members of the family Saturniidae, the Ceanothus Silkmoth does not feed as an adult, living only long enough to mate and lay eggs.  We hope your individual found a mate.

Letter 33 – Ceanothus Silkmoth

Subject: What is this moth?
Location: Carlsbad CA
March 17, 2017 11:58 am
See picture
Signature: Justin

Dear Justin,
This is a female Ceanothus Silkmoth.

Letter 34 – Ceanothus Silkmoth

Subject: Giant Moth in San Diego
Location: San Marcos, CA
March 26, 2017 10:54 am
My neighbor found this giant moth outside her door. It has 4 wings like a butterfly and I have scoured the internet to find it to no avail. A friend of mine believes it is a type of sphinx moth. But curiousity has me trying to figure this mystery out.
Signature: Michelle S

Dear Michelle,
This is a Ceanothus Silkmoth, and we have gotten several submissions this year from Southern California.  We suspect that the wetter winter led to more vegetation, and more food for caterpillars.  This will ensure better survival rates and more moth sightings.

Letter 35 – Ceanothus Silkmoth

Subject: Cecropia Moth
Location: Lompoc, California
April 14, 2017 2:24 pm
We found one of these moths, figured out the name through your page, but it doesn’t seem to want to fly away. We noticed these egg looking things on its body. What are they? Should we keep it safe in a terrarium? If so, what do they eat?
Thanks for your help!
Signature: Susan

Dear Susan,
Though this resembles a Cecropia Moth, that is an eastern species and this is a western relative, the Ceanothus Silkmoth.  Male Giant Silkmoths have more feathery antennae as that is the scent organ that allows him to locate a female through the pheromones she releases, so we believe this individual is a female.  Giant Silkmoths do not feed as adults, and they live for about a week on stored body fat.  Flying takes energy, and a female filled with eggs is much heavier, so she is reluctant to fly unnecessarily.  Often a newly emerged female will release some unfertilized eggs before attempting to fly, and we suspect that is what you have documented in your image.  Though the eggs pictured on Liang Insects are more brown, it is possible that freshly laid eggs are lighter in color.  If you keep her in a terrarium, make sure it has a screen lid.  She may attract a mate.  You might want to consider releasing her and letting nature take its course.  Again, she cannot eat. 

Ed. Note:  Since Ceanothus Silkmoths are currently in flight on the west coast, we will feature this posting for a spell.

Letter 36 – Ceanothus Silkmoth

Subject:  Moth on my wall
Geographic location of the bug:  Highland CA
Date: 01/31/2018
Time: 01:33 AM EDT
Your letter to the bugman:  We’ve seen two of these in the past two weeks. This is a picture of the first one. We found wings a few days after it left that look like they have the same pattern. It was rainy when we found the wings. We believe a bird ate it while it was at our door. It has feathery antennae and a large body.
How you want your letter signed:  Leo Wang

Dear Leo,
You are quite fortunate to have a population of Ceanothus Silkmoths near your home.  Your speculation that an individual was eaten by a bird is a distinct possibility.  Like other members of the Giant Silkmoth family, adult Ceanothus Silkmoths do not eat, and they live only long enough to mate and procreate.

Letter 37 – Ceanothus Silkmoth

Subject:  Moth
Geographic location of the bug:  Santa Rosa ca
Date: 03/13/2018
Time: 08:59 PM EDT
Your letter to the bugman:  Just wanted to share this.
How you want your letter signed:  Walt

Hi Walt,
We just responded to the comment you placed on a prior post, and we are happy you figured out how to submit images to our site.  Alas, this female Ceanothus Silkmoth does not appear to have survived the recent rains.  Hopefully she had an opportunity to mate and lay eggs before the rains hit.

Letter 38 – Ceanothus Silkmoth

Subject:  Moth
Geographic location of the bug:  Nevada City, Ca
Date: 05/07/2018
Time: 10:31 PM EDT
Your letter to the bugman:  Can you please tell us what this moth is?
How you want your letter signed:  Nancy

Dear Nancy,
This is a Ceanothus Silkmoth, and ironically, you have an image of the moth on a lilac.  Adult Ceanothus Silkmoths do not feed, but the food plant of the caterpillar is the Ceanothus, commonly called a California lilac, which is not related to the blooming lilac in your image.  The antennae on your individual leads us to believe it is a male.

Letter 39 – Ceanothus Silkmoth sighted at Camp Pendleton

Subject: large moth
Location: Southern California-San Diego-Camp Pendleton
February 1, 2013 8:27 pm
i saw this today at work just wanted to know what it was.
thank you
Signature: adam

Dear Adam,
This is a Ceanothus Silkmoth and you can tell by his especially plumose antennae that he is a male.  Ceanothus Silkmoths don’t feed as adults.  They live long enough to mate and procreate. 

Since a male and female may eclose or emerge from their cocoons many miles apart, the female releases pheromones and the male senses her with his antennae.  Once they mate, she lays eggs on California Lilac or Ceanothus and the caterpillars feed on the leaves.

Are you a Marine?  Will you be going oversees?  Are you taking a camera and internet connectivity?  Please take photos of exotic bugs and email them to our site.  Good luck.

Letter 40 – Ceanothus Silkmoth Caterpillar after all

I think I figured it out?
Location: Sonoma Mountan Range, California
December 15, 2010 2:09 am
Hi there, this is a photo I’ve sent before but didn’t hear back about…(no worries). I’ve continued to research and now I’m pretty sure it is the ceanothus silk moth larvae. I see you don’t already have a picture posted of the larvae, so I thought maybe you’d like to have it.
Signature: Mollyanne

Dear Mollyanne,
First we apologize for not responding to your earlier email, but it may have arrived on a busy day and gotten overlooked.  This is not a Ceanothus Silkmoth Caterpillar. 

This is a Royal Moth Caterpillar in the subfamily Ceratocampinae, and though there are some inconsistencies in the colors and markings, we believe it is the caterpillar of Hubbard’s Small Silkmoth as that is the only member in the subfamily known to be found in California.  

You can compare your image to the images on BugGuide an you will see the resemblance, but also the inconsistencies.  Since Hubbard’s Small Silkmoth is supposedly limited to the Eastern portion of the state and not near Sonoma, we have our doubts. 

We are going to check with Bill Oehlke to get his opinion on this puzzling mystery.  Dare we entertain the possibility that this is an unrecognized species?  Do you have any additional photos of this caterpillar?

Bill Oehlke responds with a correction
Hi Daniel,
It is Hyalophora euryalus. The shrivelled body makes the scoli seems exceptionally long.
I think it is probably fourth instar.

Ed. Note: Bill Oehlke’s response supports Mollyanne’s original identification.  This is indeed a Ceanothus Silkmoth Caterpillar, Hyalophora euryalus.

Letter 41 – Male Ceanothus Silkmoth

Subject:  Huge weird moth?
Geographic location of the bug:  Western washington
Date: 05/10/2018
Time: 03:17 PM EDT
Your letter to the bugman:  This is a very interesting huge moth/butterfly? Do I catch it or kills or let it go?
How you want your letter signed:  Bobbi

Dear Bobbi,
This is a male Ceanothus Silkmoth and they are currently flying in western states.  Here is a BugGuide image for comparison.  It is harmless and you should let it be.

Letter 42 – Spanworm on Ceanothus

Subject: What the heck is this?
Location: Bay Area, California
February 25, 2015 4:11 pm
Hello!
Can you please help me identify the creature I found today fervently attached to my ceanothus? It’s the ivory-colored stick-like thing roughly in the middle of the picture.
Thank you!
Signature: CdeP2007

Dear CdeP2007,
This is a Spanworm or Inchworm, the caterpillar of a moth in the family Geometridae.  Caterpillars in this family are often hard to distinguish from sticks, especially when they grasp a branch with their terminal prolegs, extending the body out away from the branch at an angle, much as your image illustrates.  It may be the caterpillar of a Sulfur Moth, Hesperumia sulphuraria, which is pictured on the Moths of Orange County website.