When Moths Attack Part I: Introduction and Identification

Introduction

One of the scariest things for a textile crafter is seeing a moth fly out of your precious stash of fibers and yarns. But how do you know if you have a moth infestation, how do you get rid of it, and how do you stop it from happening again?

The enemies are the webbing clothing moth, Tineola bisselliella, the case-bearing clothes moth, Tinea pellionella, the brown house moth, Hofmannophila pseudospretella, and the white shouldered house moth, Endrosis sarcitrella. Unfortunately, as humans have travelled the world they have transported moths with them. As a result, these four species are now found worldwide.

All of these moths eat proteinaceous fibers, also known as animal fibers. This category includes wool, alpaca, mohair, angora, etc. When moths are in their larval stage, the caterpillars will eat the keratin proteins that make up hair and wool. Silk is also considered an animal fiber but it is made from the protein sericin. Moth larvae don’t prefer this, but they may still have a nibble particularly if the silk is dirty and/or near wool. As the larvae eat, they leave your woolen clothes and yarn with holes.

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Moth Identification

How do you know if you have an infestation? You need to get out your magnifying glass and look for evidence from the life stages of these insects. The first stage is the egg. Moth eggs look like white dots, but are difficult to spot because of their small size.

Once the larvae hatch they appear as a white worm with a brown head. This larval stage is when moths cause damage. They feed on wool creating random small holes throughout the material. Webbing clothes moths will also create white silken tubes on textiles which can help identify them. Another telling sign of infestation is frass which is a polite way to say insect poop. Frass looks like tiny brown dots which the moths will liberally leave throughout your wool. As the moth larvae eat more of your wool and grow they can reach approximately 1/2″ (1/3 cm) long.

Once they’ve had their fill, the larvae will form a pupa or cocoon to begin their transformation into a moth. Depending on the type of moth, the pupa may be attached to the surrounding wool or not. However, since the pupa will incorporate parts of the wool the larva was eating, it will often be the same color making them sometimes difficult to spot.

The most obvious sign of an infestation is if you see an adult moth on or near your textiles. These types of moths are small, about 5 mm or 1/4″ long, and are various shades of brown. You may spot moths flying around, especially during summer and fall. However, moths don’t live very long so you will oftentimes find their earthly remains nestled in your yarn. Their bodies have a tendency to crumble and break apart, so detached wings or small patches of shiny brown dust can be another sign of moths.

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Conclusion

There are a few types of moths that eat wool and other animal fibers during their larval stage. Signs of a moth infestation include:

• Eggs as white dots
• White worms
• Small holes in wool
• Webbing
• Frass
• Pupae
• Living and dead moths

But there was too much moth information for just one post! Part II will have information on how to get rid of a moth infestation and how to prevent them from coming back.

Sources

National Trust Manual of Housekeeping: The Care of Collections in Historic Houses Open to the Public by the National Trust

MuseumsPests.net