Rusty Tussock Moth: Essential Facts and Tips

folder_openInsecta, Lepidoptera
comment3 Comments

The rusty tussock moth is a fascinating creature you might come across in nature. This moth is known for its distinctive appearance and unique life cycle. As you dive into learning about the rusty tussock moth, you’ll be surprised by the interesting information that awaits you.

In your journey to understand this intriguing insect, you’ll discover the various stages of their life cycle as well as their preferred habitats. It’s always exciting to delve into the world of these moths and uncover the secrets they hold. So, get ready to uncover all there is to know about the rusty tussock moth!

As you continue to read on, you will learn about the moth’s behavior, feeding habits, and even ways to identify them. This knowledge will enrich your understanding and appreciation for the rusty tussock moth and its fascinating existence.

Biology of Rusty Tussock Moth

Life Cycle

The life cycle of rusty tussock moths (Orgyia antiqua) consists of four stages: egg, larva, pupa, and adult moth. After mating, the female lays clusters of eggs on host plants. These eggs then hatch into larvae, which are caterpillars that feed on various deciduous and evergreen plants. As they grow, the caterpillars molt several times before transforming into a pupa. Following the pupal stage, an adult moth emerges to complete the life cycle1.

Physical Characteristics

Rusty tussock moth adults exhibit sexual dimorphism, meaning males and females have distinct physical features. Adult males have black, brownish, and gray coloration with a whitish blotch and brown band on each forewing2. They possess a wingspan of around 30-35mm3. In contrast, female moths are flightless, have reduced wings, and are larger than males4. The larvae sport a black body with numerous gray to tan hairs, and projecting tufts of black hair on their front and rear5.

Unique Traits

  • Orgyia antiqua larvae have distinct hairs called setae on their body1.
  • Adult moths showcase sexual dimorphism4.
  • Larvae feed on many different deciduous and evergreen plants5.

Behavior and Habits

Rusty tussock moth larvae are known to be gregarious early in life, feeding on one or a few closely associated leaves. As they mature, they become more solitary and spread out to feed individually or in smaller groups6.

Adult moths have a unique behavior where the males actively search for females using their comblike antennae to detect pheromones. After mating, the female lays eggs and covers them with hairs from her body for protection7.

Role of Vapourer Moth

Rusty tussock moths, also known as vapourer moths, play an essential role in maintaining the balance of their ecosystem. They serve as a food source for several predators, such as birds and other insects. As herbivores, they help with the decomposition of plant material, contributing to the nutrient cycle8.

Habitat and Distribution

General Habitats

Rusty tussock moths (Orygia antiqua) are commonly found in forests and woodlands, where they inhabit many different deciduous and evergreen plants. Their natural habitat includes a variety of tree species, such as birch and Sitka spruce trees. These moths prefer environments with an abundance of host plants for their larvae to feed on.

North American Distribution

Rusty tussock moths have a widespread distribution across North America. They can be found in various regions, including eastern and central United States, as well as parts of Canada. You might come across these moths in your local woodland areas or even your garden, where they can cause damage to their host plants.

Host Plants

The larvae of rusty tussock moths feed on a wide range of host plants. Some of the most common host plants include:

  • Birch trees
  • Sitka spruce trees
  • Oak trees
  • Poplar trees
  • Willow trees

These caterpillars are not very picky and will feed on other deciduous and evergreen plants as well. However, their feeding habits can cause significant damage to the foliage of these plants, which is a concern for gardeners and forest conservators alike.

Now that you are familiar with the habitat and distribution of the rusty tussock moth, it is essential to keep an eye out for these insects in your surroundings. By being aware of their presence and knowing their preferred host plants, you can better manage their impact on the environment.

Potential Negative Interactions

Effects on Humans

The rusty tussock moth can cause skin irritation in some individuals. This is due to contact with the setae, or hairs, present on the caterpillar stage of the moth. When you touch these hairs, they can break off and penetrate the skin, causing a reaction.

To reduce the risk of irritation:

  • Be cautious when handling vegetation where the caterpillars may be present.
  • Wear gloves or use a tool when removing the caterpillars or their egg masses.

Effects on Vegetation

The rusty tussock moth’s caterpillars feed on a wide variety of plants. Heavy infestations can lead to severe defoliation and, in some cases, even the death of the plant. Some potential effects on vegetation include:

  • Loss of leaves, which can impact a plant’s overall health and vitality.
  • Damage to young trees and shrubs, especially during an outbreak of the moth.
  • Potential weakening of the ecosystem due to plant loss and reduced habitat availability for other organisms.

To help protect your vegetation:

  • Monitor the plants in your garden or property for signs of infestation.
  • Remove egg masses and caterpillars where possible.
  • Seek professional advice or consider using an approved pesticide if infestations are severe.


Lymantriidae Lineage

The rusty tussock moth, also known as Orgyia antiqua, is part of the Lymantriidae family, which is a group of moths with over 2,500 known species. These moths are famous for having hairy, colorful caterpillars. Within the Lymantriidae lineage, you’ll find tussock moths exhibit the following features:

  • Hairy caterpillars
  • Mostly nocturnal adult moths
  • Diverse colors and patterns

For example, the hickory tussock moth is another species in this lineage that, like Orgyia antiqua, goes through one generation per year.

Erebidae Lineage

In recent years, taxonomic studies have moved the Lymantriidae family under the superfamily Noctuoidea, within the Erebidae family. This new classification groups tussock moths with approximately 25,000 species of other moths found worldwide. Some common characteristics of the Erebidae lineage are:

  • Adults with bipectinate (comb-like) antennae
  • Flightless or reduced-winged females
  • High diversity in appearance

Within the Erebidae lineage, the rosy maple moth (Dryocampa rubicunda) is an example of a species related to the rusty tussock moth, sharing a similar lifestyle and vivid color variations.

Here’s a brief comparison table highlighting the differences between the Lymantriidae and Erebidae lineages:

Lineage Notable Features Example Species
Lymantriidae Hairy caterpillars, mostly nocturnal adults, diverse colors Hickory tussock moth (Lophocampa caryae)
Erebidae Bipectinate antennae, flightless or reduced-winged females, high diversity in appearance Rosy maple moth (Dryocampa rubicunda)

By understanding these classifications, you can better appreciate the unique characteristics and diverse nature of moths, including the fascinating rusty tussock moth.

Caterpillar Populations

Rise in Populations

In recent years, populations of tussock moth caterpillars, like the hickory tussock moth caterpillar, have been observed to increase. This rise could be due to a variety of factors such as changes in weather patterns, availability of host plants, and lack of natural predators. Fluctuations in their numbers are a normal part of their life cycle and can vary from year to year.

For example, tussock caterpillars were abundant in Maine in 2011 where they caught people’s attention due to their itchy hairs. Their populations can boom and then recede, just like when you faced a sudden upsurge of mosquitoes in your backyard.

Impact on Ecology

Tussock moth caterpillars can cause an impact on the local ecology. When their populations rise significantly, they may defoliate their host plants, causing stress to the plants and decreasing the availability of food for other insect species. Moreover, an increased abundance of these caterpillars can have a ripple effect on other organisms in the ecosystem, including predators that rely on them as a food source.

For instance, increased numbers of caterpillars in an area can attract certain bird species, leading to changes in the local bird community, or they can deplete the plant life, affecting the habitat of other insects.

Pros of Tussock Moth Caterpillars:

  • Provide a food source for predators
  • Contribute to the ecosystem’s natural balance

Cons of Tussock Moth Caterpillars:

  • Potentially cause allergic reactions due to their hairs
  • Defoliate trees and other host plants when populations are high
Pros Cons
Tussock Moth Caterpillars Food source for predators, contribute to ecosystem balance Allergic reactions from hairs, defoliation of host plants

Remember, it’s essential to keep an eye on changes in caterpillar populations and take appropriate measures, such as planting diverse species and applying natural insecticides like Bt (Bacillus thuringiensis), if needed to maintain a balanced ecosystem in your surroundings.


In conclusion, the rusty tussock moth is a defoliator that feeds on a variety of different deciduous and evergreen plants. These pests can cause significant damage to the plants, resulting in reduced growth and vitality. It is essential to be aware of the moth’s presence and to keep an eye out for the characteristic larvae with their gray to tan hairs and black tufts.

The rusty tussock moth has been known to cause outbreaks and extensive defoliation, as seen in the Matanuska-Susitna Borough since 2020. However, as of 2022, the damage caused by this moth appears to have significantly decreased. To manage and prevent the spread of these pests, it is crucial to regularly monitor your plants, take appropriate control measures, and maintain a healthy garden environment.

When dealing with the rusty tussock moth, please remember to:

  • Regularly inspect your plants for larvae and signs of damage
  • Use appropriate pest control methods as needed
  • Promote a healthy garden ecosystem to minimize the chances of an outbreak

Although the rusty tussock moth and ice may not seem immediately relatable, both can pose risks to plants in different ways. While the moth damages plants through defoliation, ice can cause breakage, damage to roots or branches, and even kill off sensitive plant species. Being aware of these threats and knowing how to protect your plants from both moth damage and ice is essential for maintaining a thriving garden.

Keep up your friendly gardening efforts and continue to learn about the various pests and environmental factors that can impact your plants. By staying informed and proactive, you can create a flourishing garden that will bring joy for years to come.


  1. Tussock Moths: UC IPM 2

  2. Banded Tussock Moth: Missouri Department of Conservation

  3. Tussock Moths: UK Moths

  4. Tussock Moths: Missouri Department of Conservation 2

  5. Tussock Moths: UC IPM 2

  6. Hickory Tussock Moth Caterpillar: Penn State Extension

  7. Life Cycle of Tussock Moths

  8. Role of Moths in the Ecosystem

Reader Emails

Over the years, our website, 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 – Rusty Tussock Moth Caterpillar in Alaska


Location: fairbanks, ak
July 25, 2011 8:41 pm
hi! i see these little guys in my garden all the time. just curious what kind of caterpillar? it is. it is black with 4 yellow knobs on its back. yellow tufts of hair, 2 antennae on top, 2 on the side, and one on the bottom.
Signature: just curious

Rusty Tussock Caterpillar

Dear just curious,
WE don’t get many insect images from Alaska, and it is always exciting when we do.  This is the Rusty Tussock Moth Caterpillar,
Orygia antigua.  The Forest Health Conditions in Alaska 2003 Google Books website indicates: Rusty Tussock Moth populations were high this year on birch, willow, and blueberries.  Even though larval populations were high, levels of defoliation were low.  The dark hairy caterpillar is about 3 cm long with four yellow ‘tussocks’ of hair along the back, two tufts of dark hair near the head and one more at the rear.  The adult male is an erratic-flying-rusty-brown moth with a white dot and a light brown band on each forewing.  the female is flightless.  The biggest concern from the public was the likelihood of the caterpillar hairs causing irritation and rashes to blueberry pickers, as was published in a local newspaper.  Individuals and medical professionals from rural Alaska made several inquiries concerning the caterpillars’ potential for causing dermatitis.  Medical entomology reference texts indicate that their long hairs, left on plant material, can cause irritation to exposed skin even when not directly exposed to the live caterpillars.”  We rotated your image to make better use of our horizontal format.  The moth is also known as the Common Vapourer according to Inmagine.

Letter 2 – Rusty Tussock Moth Caterpillar from Alaska


Subject: Name that caterpillar from Alaska please
Location: Eagle river Alaska
August 11, 2014 3:39 pm
What is this ? We saw it on our strawberry plants !
Signature: Melissa

Tussock Moth Caterpillar
Rusty Tussock Moth Caterpillar

Dear Melissa,
This looks like a Tussock Moth Caterpillar in the genus
Orgyia.  We believe it is the Rusty Tussock Moth Caterpillar, Orgyia antiqua, which according to BugGuide has been sighted in Alaska.  BugGuide also notes “Caterpillars are generalist feeders on the foliage of flowering trees in the Rosaceae, Fagaceae, Ericaceae, and Salicaceae” and strawberry is in the family Rosaceae.  Finally, BugGuide indicates:  “Native to Europe but now found throughout North America, Europe, and parts of Africa and Asia” which makes it an invasive, exotic species.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. 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.

    View all posts
  • 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.

    View all posts
Tags: Tussock Moths

Related Posts

3 Comments. Leave new

Leave a Reply

Your email address will not be published. Required fields are marked *

Fill out this field
Fill out this field
Please enter a valid email address.
You need to agree with the terms to proceed