Caterpillars That Darken in Color and Form Webs

earthworm in dirt

We recently received this message from one of our readers, “What are these worms and what can we do? We’ve been finding what look like white immature ones, and then it seems that they form a web and darken in color. We think they are some form of moth larvae. We are living in a house in Ontario, Canada that has been vacant for about four months.”

Sadly, our reader didn’t send a photograph of the mysterious creatures. Without a photograph it will be difficult, if not impossible, to figure out which specimens our reader is dealing with. Therefore, we will answer our reader’s questions with some information and general advice rather than specific instructions.


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Based on our reader’s message, we agree that she is likely dealing with some sort of moth larvae. The life of a caterpillar, which is another way to describe the larva of a moth or butterfly, revolves around eating. In fact, a caterpillar does nothing but eat for 2-4 weeks beginning when it emerges from the egg and lasting until it pupates and transforms into a moth or butterfly. During these 2-4 weeks of constant eating, a caterpillar grows so much that its skin becomes too stretched to expand any further. When this happens, the caterpillar will replace its skin with a larger one that allows it to continue eating and growing. So, the creature our reader found could be growing larger and darkening in color slightly as it changes its skin.

Now, what about the web that our reader mentioned? Well, while all caterpillars form some sort of cocoon to transform into a moth or butterfly, not all caterpillars are able to create silk. Most moth larvae can spin silk, while most butterfly larvae can not. Moth larvae spin thick silk cocoons to undergo the big transformation, but butterfly larvae hang upside down and create a tough outer shell that resembles a leaf hanging from a branch. So, we believe the creatures our reader found are moth larvae rather than butterfly larvae. We know this is a bit confusing because both can be referred to as caterpillars.

We don’t know the exact species of moth larvae our reader is dealing with, but we do have some suggestions on how to deal with their presence. Since the house hasn’t been lived in for a few months, we think giving it a proper cleaning should help get rid of these caterpillars. Although we don’t know their specific food source, we believe that cleaning all of the rooms thoroughly (or at least the rooms where the caterpillars are living) will effectively eliminate their food source. She should dust, sweep, vacuum, and wipe down all surfaces. In addition to cleaning, she can prevent other organisms from sneaking into her home by sealing up all windows, doors, and vents! We hope our reader is able to say goodbye to these caterpillars.

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To wrap up, a reader wrote to us about some moth larvae that are living in her new home. Although we weren’t able to identify the specimens, we don’t think these creatures are harmful, and we believe she should be able to get rid of them by cleaning. If our reader is still curious about the exact species she is dealing with, we invite her to send us a photograph!

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Caterpillars That Darken in Color and Form Webs
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Caterpillars That Darken in Color and Form Webs
Description
A reader wrote to us about some moth larvae that are living in her new home. Although we weren't able to identify the specimens, we don't think these creatures are harmful, and we believe she should be able to get rid of them by cleaning.
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Author: Worm Researcher Dori

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