Complete Guide To The Ailanthus Webworm Moth
Mother Nature really surprises me sometimes.
I’ve been journalling about nature and the creatures I see for nearly two decades. It’s pretty rare for me to encounter a totally new-to-me species. But these colorful insects flummoxed me. Totally.
And yet, nature is astonishingly diverse, and operates on its own schedule. I’ve found I have to be in the right place at the right time to see certain creatures.
Enter my first encounter with Ailanthus Webworm Moths (Atteva aurea).
I was out hiking, scanning for animals as always, and hadn’t seen much. Summer was fading into fall, temperatures were dropping, and I’d noticed a sharp drop-off in the number of creatures already. As I walked past a large stand of tall, weedy plants topped with hundreds of tiny white flowers, a tiny speck of orange caught my eye.
Peering closer, I saw a tiny shape crawling slowly over the white flowers. It was tiny and at least 15 feet away from where I was standing. All I could really see was a blur of orange. But it was moving and that’s always good enough for me. I took the best photographs I could manage and hurried home.
Thanks to my trusty telephoto lens, my camera captured the detail my eyes couldn’t see and showed me a tiny but visually striking insect. And thanks to my trusty collection of field guides, I identified it as an Ailanthus Webworm moth (Atteva aurea) – an insect known to science, but one that I’d never before seen.
An excellent reminder that nature always offers curious people something exciting to see!
Fun Facts About Ailanthus Webworm Moths
- Ailanthus Webworm moths are great mimics.
- Their folded wings look very much like tiny pieces of millefiori, the patterned Italian decorative glass that resembles “a thousand flowers”.
- The way they fold their wings at rest also make them look like beetles at first glance.
- In flight, these moths look like wasps.
- Despite being only about the length of a grain of wild rice, Ailanthus Webworm Moths (Atteva aurea) are actually one of the larger species of “microlepidoptera”. Most are so small as to go almost entirely unnoticed.
- This species feeds on “tree-of-heaven” trees(Ailanthus altissima). These trees can grow 100 feet (30 meters) high and develop trunks 3 feet (1 m) in diameter (Ailanthus, 2020).
- The first Tree-of-Heaven was planted in Philadelphia in 1784. The species spread quickly across the eastern United States and has now even reached southern Texas (Wilson et al. 2010).
Overview of Ailanthus Webworm Moths
Classification of Ailanthus Webworm Moths
| Kingdom | Animalia |
| Phylum | Arthropoda |
| Class | Insecta |
| Order | Lepidoptera |
| Family | Yponomeuti- dae (the Ermine moths) |
| Genus species name | Atteva aurea |
Ailanthus Webworm moth classification has changed over the years. Scientists used to refer to this species as Atteva punctella and many field guides still do. But scientists renamed it to Atteva aurea in 2010 based on DNA research (Wilson et al. 2015).
Physical Appearance of Ailanthus Webworm Moths
Ailanthus Webworm Moth Eggs
I wasn’t able to find any information about Ailanthus Webworm moth eggs. I suspect that this is because they are extremely tiny, given the small size of the adults, and go unnoticed.
Ailanthus Webworm Moth Caterpillars
I wasn’t able to find any information about Ailanthus Webworm moth caterpillars, although one reference I checked includes them in their “needleminer” section (Leckie and Beadle, 2018).
Needleminers tunnel between the tough epidermal layers of a leaf’s surface to feed on the soft inner tissue. They often leave characteristic tracings across the leaf surface.
Ailanthus Webworm Moth Adults
Adult Ailanthus Webworm moths grow to 0.4-0.6 inches (10-16 mm) long – only about as long as a grain of wild rice. Their wings span a little more than 1 inch (27-29 mm) (Milne and Milne, 1980).
Despite being so small, they are easy to see, thanks to bright orange and white banded fore wings. Their brightly colored fore wings hide dark hind wings when not in flight (Leckie and Beadle, 2018).
Ailanthus Webworm Moth Habitat
Ailanthus Webworm moths (Atteva aurea) live throughout the southeastern United States. Adults fly between the beginning of April to mid-November, although their density varies significantly across different regions.
These moths follow their food plants. Some areas grow large numbers of their food plants, while others grow very few.
Ailanthus Webworm Moth Lifecycle and Reproduction
Like all lepitopterans, Ailanthus Webworm moths grow through four life stages: egg, larva, pupa, and adult. Each stage is entirely distinct, with different appearances and behaviors.
Larval moths and butterflies are called “caterpillars”. The term used for the pupal form differs between the two types of insects. Butterflies form “chrysalids” and moths form “cocoons”.
But both forms consist of a hardened, waterproof shell that surrounds the caterpillar. This outer covering protects it while the insect’s tissues dissolve and rebuild into the winged adult form.
Ailanthus Webworm Moth Food and Feeding Behavior
Larval Host Plants
Ailanthus Webworm Moth caterpillars make communal webs on the foliage of ailanthus trees (Eaton and Kaufman, 2007). Also referred to as “tree of heaven”, Ailanthus altissima is an invasive ornamental tree native to East Asia.
Adult Host Plants
I could find no specific information about the feeding behavior or food plants of adult Ailanthus Webworm Moths.
However, the one and only time I’ve encountered these insects after years of exploring North Carolina’s wildlife was in a thick patch of flowering weeds, which I think was White Snakeroot (Eupatorium rugusum).
White Snakeroot plants grow many large flower clusters, made up of hundreds of tiny individual flowers. The area I explored today contained many, many snakeroot bushes. And Ailanthus Webworm Moths crawled over nearly every flower cluster. They were everywhere and I’ve never seen anything like it.
Predators and Threats to Ailanthus Webworm Moths
I was very curious to find out what animals prey on these Ailanthus Webworm Moths because the moths are so brightly colored.
Many insect species have evolved bright colors to warn predators against attacking them. Orange, white, black, red, and yellow are the colors most associated with this visual defense mechanism.
Some insects back up the warning with legitimate chemical defenses. These species either manufacture chemical toxins that can poison predators through their natural metabolisms or sequester these chemicals from other sources.
Other species evolved bright warning colors but the signal is a bluff. Predators may avoid attacking edible insects because they’ve learned to associate bright colors with unpleasant side effects.
An Open Question
Unfortunately, I could not find any information about whether this moth species protects itself by being toxic to predators or whether its coloration is a bluff.
Many moths are active at night, when colors are washed out or invisible. This is why bats, which are major predators of moths, hunt by bouncing high-frequency sound waves off flying objects rather than hunting by sight.
But I spotted these Ailanthus Webworm Moths during the day, before sunset. I spotted them despite their small size because their orange and white coloring stood out so clearly against the white flowers. So I’m sure that known predators of moths and butterflies, such as birds and assassin bugs, could also find them easily.
The open question is whether they would bother. If anyone knows the answer to this question, please leave it in the Comments section below!
Final Thoughts
Unfortunately, and as often happens, I didn’t have very much time at all to observe these tiny, colorful insects. When I returned to the stand after a day, I couldn’t find even a single moth.
Only the webworms themselves know if they flew off to feed somewhere else or just died off en masse. Regardless, the transition from an abundance of bright orange moths to none at all was abrupt, surprising, and disappointing.
My Nature Journal Summary
| Habitat Explored | Thick brush along a man-made flood control lake. |
| Temperature | 75ยฐ F; 24ยฐ C |
| Weather | Broken clouds |
| Wind | 8 mph from 60ยฐ ENE to WSW |
| Humidity | 60% |
| Species Encountered | Ailanthus webworm moth (Atteva aurea) White snakeroot (Eupatorium rugosum) |
Where to Go From Here
Join the conversation! Please share your experiences, knowledge, or observations in the comments.
References
Ailanthus 2020. Abingdon: RM Education, Ltd.
Eaton, Eric R., and Kenn Kaufman. 2007. Kaufman Field Guide to Insects of North America. New York, NY: Mariner Books, Harper Collins.
Leckie, Seabrooke and David Beadle. 2018. Peterson Field Guide to Moths of Southeastern North America. New York, NY: Houghton Mifflin Harcourt Publishing Company.
Milne, Lorus, and Margery Milne. 1980. National Audubon Society Field Guide to Insects and Spiders: North America. New York, NY: Chanticleer Press, Inc.
Wilson, John, Jean-Franรงois Landry, Daniel Janzen, Winnie Hallwachs, Vazrick Nazari, Mehrdad Hajibabaei, and Paul Hebert. 2010. “Identity of the Ailanthus Webworm Moth (Lepidoptera, Yponomeutidae), a Complex of Two Species: Evidence from DNA Barcoding, Morphology and Ecology.” ZooKeys 46: 41-60.
