Ermine Moth: Comprehensive Guide for Curious Minds

The Ermine Moth is a small, fascinating insect found in gardens and orchards, known for its unique appearance. With wingspan lengths of 1.2-3 centimeters, these moths bear a striking resemblance to the Ermine, a mammal that looks like a weasel, giving them their distinctive name. Members of the Yponomeutidae family, these tiny creatures can be a captivating sight.

These moths are not just found in North America but also have origins in Eurasia. For example, the Apple Ermine Moth is a species that originated there and has spread to areas like British Columbia, Washington, and Oregon. The larvae of this particular moth feed mainly on leaves, which can sometimes lead to defoliation of entire trees during severe infestations.

Ermine Moths impact the environment in various ways:

• They act as pollinators for certain plants.
• Their larvae can sometimes help control invasive plant species.
• Predators such as birds, spiders, and other insects rely on these moths for food.

Though these moths can be delightful to observe, it’s essential to monitor their populations, as they can cause harm to certain plants and trees in the garden or orchard. Keep an eye out for signs of their presence, and if needed, seek advice on controlling their populations without harming the ecosystem.

Identification and Distribution

Species of Ermine Moths

Ermine moths belong to the Yponomeutidae family and have a wingspan length of 1.2-3 centimeters. Some common species are:

• Small ermine moths
• White ermine

These moths have colors resembling ermines, a European or North American mammal that looks like a weasel.

Habitat

Ermine moths can be commonly found in gardens, orchards, and forest edges. They are distributed across temperate and subtropical regions.

Detecting the presence of ermine moths can be done by using traps. For example, bait wing traps with the commercially available ermine moth pheromone and place them in apple or crab apple trees.

Comparison Table

• Note: The size and coloration may vary between individuals and regions.

Life Cycle and Biology

Eggs and Larvae

Ermine moths, specifically Yponomeuta padella, begin their life cycle as eggs. Females lay clusters of eggs on hawthorn plants during the summer months. Once hatched, the larvae (caterpillars) start feeding on the leaves.

Characteristics of eggs and larvae:

• Tiny, oval-shaped
• Laid in clusters
• Hatch in about 10 days

Caterpillar and Web

Ermine moth caterpillars are known for creating communal silk webs. These webs serve as protection from predators and sun, as well as a means to trap moisture. They can cover entire trees or hedges, giving a dramatic appearance.

Caterpillar features:

• Distinctive black spots on white or yellowish body
• Feed on hawthorn leaves
• Create silk webs

Pupating and Adult Moths

After sufficient feeding and growth, caterpillars move to the tree trunk or nearby structures to pupate. After two to three weeks, adult moths emerge from the pupae.

Adult moths:

• White, covered in tiny black spots
• Wingspan of 20-27 mm
• Night-active pollinators

Here is a comparison of the different stages:

Host Plants and Feeding Behavior

Common Plants

Ermine moths, belonging to the family Yponomeutidae, are known to feed on various host plants. Some common plants that serve as their habitat include:

• Trees like apple and blackthorn
• Shrubs and hedges

Both the Y. evonymella and Y. cagnagella species of ermine moths utilize these host plants in their life cycle.

Damage to Trees and Shrubs

Ermine moths can cause significant damage to trees and shrubs in their feeding process. They feed on both the leaves and the bark. Typically, ermine moths focus on:

• Consuming leaves, causing defoliation
• Attacking the bud and bark, leading to structural damage

Here’s a table comparing the damage caused by ermine moths on different parts of the plants:

The extent of the damage caused by ermine moths depends on the specific host plant, the moth species, and the population size. Despite their destructive feeding behavior, these moths also play a part in the pollination process, contributing to the ecosystem’s balance.

Natural Predators and Threats

Birds and Insects

Ermine moths, like other insects, face various predators in their environment. Birds, for example, are significant predators that target various life stages of moths. Some bird species may feed on adult moths, while others target caterpillars or eggs.

Insects can be predators too, for instance, green lacewing larvae are known to consume smaller caterpillars or beetle larvae. Parasitic wasps prey on caterpillars, injecting their eggs into the host, which later hatch and feed on the caterpillar from the inside.

Spiders and Other Predators

Spiders are a common predator of moths in various life stages. They capture the moths in their webs or hunt them down on the ground. Other arthropods such as centipedes or predatory beetles can also be a threat to moths and their larvae.

Given these various predators, evolution has led ermine moths to develop different strategies to increase their survival rates, such as camouflage or being active at night to avoid diurnal predators.

To summarize, ermine moths face several predators in their environment, including:

• Birds: targeting adult moths, caterpillars, or eggs
• Insects: e.g., green lacewing larvae and parasitic wasps
• Spiders: capture moths in their webs or hunt them
• Other arthropods: centipedes or predatory beetles

Gardeners may find it helpful to attract some of these natural predators, such as birds or lacewings, as a method of biological control to manage moth populations in their gardens.

Signs and Symptoms of Infestation

Webbing and Tents

Ermine moth infestations in gardens can often be identified by the presence of webs and tents. These are typically found on:

• Trees
• Shrubs
• Leaves

These silky webbings and tents can vary in size and are created by the larvae to protect themselves and their food sources.

Examples of common trees and shrubs affected by ermine moth infestations:

• Apple trees
• Cherry trees
• Hawthorn shrubs

Defoliation

Another sign of ermine moth infestation is defoliation. This occurs when the moth larvae feed on leaves, leading to:

• Partial or complete defoliation
• Reduced plant growth

Partial defoliation is characterized by holes or missing portions of leaves. Complete defoliation, however, leaves only the skeletal remains of the leaf structure.

Comparing webbing and defoliation symptoms:

In summary, ermine moth infestations can be detected through the presence of webbing and tents on trees, shrubs, and leaves, as well as signs of defoliation, like holes and reduced plant growth.

Control and Management

Non-Chemical Solutions

Ermine moths can be managed in gardens without chemicals by using a few non-chemical methods:

• Pheromone Traps: Setting up pheromone traps can help capture male ermine moths, reducing breeding and infestation.
• Manual Removal: Remove nests and silken webbing by hand from May to June when they’re most likely to be noticed.
• Natural Predators: Encouraging birds and other natural predators can help keep the ermine moth population under control.

Chemical Solutions and Insecticides

If non-chemical solutions aren’t enough, various chemicals and insecticides can be used in ermine moth control:

• Bacillus thuringiensis (Bt): This natural soil bacterium can be used as a biological insecticide against caterpillars. It is harmless to humans, pets, and pollinating insects.
• Lambda-cyhalothrin: A synthetic pyrethroid insecticide that can be used to control ermine moth larvae.
• Deltamethrin: Another synthetic pyrethroid, often used as a contact insecticide.
• Acetamiprid: A neonicotinoid insecticide that is effective against ermine moths but can be harmful to pollinating insects.

Example of a comparison table:

When using chemical control, it’s essential to follow the product’s instructions carefully and apply treatments as recommended to minimize any potential harm to non-target species. Avoid using insecticides when pollinating insects, such as bees, are active in the area.

Specific Ermine Moth Species

Apple Ermine Moths

Apple Ermine Moths, also known as Yponomeuta malinellus, are a type of Ermine Moth that primarily infests fruit trees. These moths have a wingspan of about 1.2-3 centimeters, with their hindwings being slightly smaller than their forewings¹. Apple Ermine Moths are pests in many orchards and can cause severe damage if not managed properly. To detect them, you can use pheromone traps placed in apple trees².

Characteristics:

• Wingspan: 1.2-3 cm
• Primarily infest fruit trees
• Hindwings smaller than forewings
• Pest in orchards

Pros and Cons of Trapping:

• Pros: Monitors moth population, helps with pest control
• Cons: Requires regular lure changes

Spindle and Bird-Cherry Ermine

The Spindle Ermine Moth (Yponomeuta padella)³ and Bird-Cherry Ermine Moth are two other species of Ermine Moths. They can create nests that resemble spider webs, weaving their silk to connect leaves and branches together. These moths are sometimes mistaken for butterflies due to their small size and colorful wings.

Features:

• Create nest-like silk webs
• Can be confused with butterflies
• Found on spindle and bird-cherry trees

Comparison Table

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 – Ailanthus Webworm Moths

Subject:  insect ID
Geographic location of the bug:  south texas
Date: 02/04/2019
Time: 08:02 PM EDT
Your letter to the bugman:  several of these are on one of our 4 year old grapefruit trees
How you want your letter signed:  tony p.

Dear Tony,
These are Ailanthus Webworm Moths and they will not harm your grapefruit.  They are seeking nectar from the blossoms, so they might actually be pollinating more fruit for you.  The Ailanthus Webworm Moth is a native North American species that has adapted so that caterpillars feed on the leaves of the scourge, the Tree of Heaven, but alas, feeding on just the leaves does nothing to curb the spread of this invasive “weed” tree.

Letter 2 – Ermine Moth

from Michigan
(08/03/2004)
I found this bug and it is orange with really light yellow or cream colored squares
William

Sorry,
too vague a description.

hi me again i just took pics of it so if you know what kind of bug it is can you please tell us we just don’t know

Hi William,
Thanks for sending a beautiful photo of an Ermine Moth, either Atteva aurea or Atteva gemmata. The caterpillars eat ailanthus leaves. They are reportedly from the south, but we just received a letter from a reader who sited some in Long Island New York. Here is the letter:

(08/03/2004) A. aurea or A. gemmata
i will get a picture the next time i find one but you can extend their range to Long Island, NY….they are around my screen door in the morning and i was using your site to find out what they were as i had never seen anything like them (big thank you). i’ve given a few female dobson flies to my Jackson’s chameleon….before i found your site i would run from them, now i go hunting for them…thanks
Danny D

Letter 3 – Ermine Moth

White spotted moth
Hi and thanks for your time.
My name is Ian Thomson from Milwaukee, Wisconsin. I came home the other day to see a moth I haven’t seen before perched on my porch door. It is appx. 3/4″ long and is mostly snow white with small black spots. It seems very well camouflaged for my white door trim, but it doesn’t seem especially well suited for the wild in Wisconsin this time of year. I am curious if you have any idea what this fella may be, and if it may be unusual for this area, or if I just haven’t been looking hard enough. The moth is hanging upside down, but I rotated the photos right side up. Also, apologies for the photo quality–my digital camera is not especially sophisticated and refuses to focus on near objects. I did some brief searching and saw a giant leopard moth, but this seems much smaller with less dark spotting. Perhaps a cousin? Please let me know your thoughts as I am very curious. Thank you much for your time, I look forward to your reply!
Ian Thomson

Hi Ian,
Your moth is in the Ermine Moth family Yponomeutidae and in the genus Yponomeuta. We located it on BugGuide and it does not have a common name.

Letter 4 – Ermine Moth: Atteva species

The bug is black with orange and yellow spots. It flys although it looks too small to be a butterfly. Could it be a moth? Please see attached for more details.
Thank you
Katie

Hi Katie,
Holland’s Book of Moths does little more than identify your photo as a member of the genus Atteva, either Atteva aurea or Atteva gemmata. Both are small moths found in the South. Of the two, A aurea has the larger range, being distributed in the Gulf States southward and westward into Mexico and still further South. A. gemmata is found in the warmer parts of Florida. These moths are part of a small Family Yponomeutidae, known as Ermine Moths. The larvae of Atteva aurea feeds on ailanthus leaves.

Letter 5 – Flower Power: Moths and Flies Attracted to Snowball Viburnum

Snowball Viburnum Denizens
Location: Trumbull, CT
August 29, 2011 6:58 pm
I tried to look up both of these insects, but I only found one. The first is an ailanthus webworm moth, but I don’t know what the second one is. I occasionally find interesting insects on the snowball viburnum bush in my front yard.
Signature: Chuck

Dear Chuck,
Congratulations on having successfully identified your Ailanthus Webworm Moth.  Folks of a certain age and those who think flower power was the apex of 20th Century style will likely respond to the repetitious patterns and play on scale evident in this lush photograph.  Your other insect is a Feather Legged Fly, Trichopoda pennipes, a member of the Tachinid Fly family Tachinidae.  Tachinid Flies have larvae that are internal parasites of other insects, arachnids and certain members of other arthropod orders.  In the case of the Feather Legged Fly, the host insect is a Stink Bug.  Here is the BugGuide page on this species.

Letter 6 – Pied Smudge from UK

Subject: Insect
Location: Lancashire
December 23, 2013 3:40 am
This insect was found on garage forecourt (tarmac)
in Nelson-Lancashire
I cannot find an identification anywhere: can you please help
Signature: Curious

Dear Curious,
This is a Moth, but we are having trouble determining its identity.  You sent the email request today, but when did you observe the moth?  Many times people take photos in the summer, but neglect to send the photos until the boredom of winter sets in.  With additional free time to clean up unfinished business, many summer photos are sent to us in December.  If this moth actually appeared in December, that would be very helpful information.  The first lead we got was an interesting blog entitled 1000 for 1KSQ with the tag “a blog about the nuts and bolts of biodiversity – finding LOTS of species.  But how many can you find in just a single 1km square?”  Number 940 is Ethmia bipunctella (moth), a black and white moth that looks similar to your moth.  Armed with a name, we learned on UK Moths that the family Ethmiidae has several black and white moths found in the UK, however, none looks exactly like your individual.  BugGuide considers that to be a subfamily of the Grass Miner Moth family Elachistidae.  We are not satisfied that we have an accurate identification, and you might try browsing through the images on UK Moths to correctly determine your distinctive moth’s identity.
Well, our diligence paid off and we finally stumbled upon the Pied Smudge, Ypsolopha sequella, on Norfolk Moths when we included the term “pied” in our UK search.  It is listed as “Local.  Highly distinctive species.  Rests by day on trunk of trees. comes to light.”  UK Moths states:  “This highly distinctive species, with its pied appearance, is locally widespread in wooded areas over England and Wales.  It flies at night in July and August, and comes to light.  The larvae feed mostly on species of Acer, particularly field maple (A. campestre).”

Thank you Daniel;
I am delighted that you have identified  my moth, without a doubt.
You are right too about the winter gloom being catch up time; this moth was photographed on the 22nd July 2013 at 10.30 in the morning.
We live close to a small wooded area of mostly Sycamore and Ash; there are no Acer.

Letter 7 – Sun Moth from Mexico

Subject: Whats that bug?
Location: Puebla Mexico
August 17, 2016 4:51 pm
Hello bugman , I was searching over internet in a lot of entomology sites and pics trying to find what kind of bug is this that I found over a “Mirabilis Jalapa” flower yesterday morning in the Mexican state of Puebla.
it is more or less 1 inch in size with 6 black and silver spoted legs, a pair of long antennas ending in a little bright silver part.
The body was coloured in a light orange tone filled whit brilliant and metalic silver spots, the back of thorax was covered with a kind of armor of the same silver brilliant under the sun metalic color. with a pair of wings .
Thak you a lot for your help and support all will be very appreciated.
Tomas K.
Puebla Mexico
Signature: Tomas K.

Dear Tomas,
We thought this little beauty resembled an Ermine Moth so we searched the superfamily Yponomeutoidea, Ermine Moths and Kin on BugGuide and we located a very similar looking moth identified as a Sun Moth in the family Heliodinidae.  We located another similar looking individual on Nature Watch, also identified only to the family level.  We returned to BugGuide and learned that three different genera in the Sun Moth family all look quite similar, so we hope a family identification will suffice as we do not believe we will be able to provide a species name or even a genus name with any certainty.  We have a single Sun Moth on our site, but it belongs to the family Castniidae, so will be classifying your individual with the Ermine Moths.