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