Where Do Inchworms Come From? Unraveling Nature’s Tiny Secret

Inchworms, also known as cankerworms or loopers, are the larval stage of several species of geometrid moths. Interestingly, these small creatures play a significant role in nature as they assist in the decomposition of plant material. You might have seen these fascinating critters inching along leaves and branches, but have you ever wondered where they come from?

To better understand the origins of inchworms, it’s essential to delve into their life cycle. Adult geometrid moths lay their eggs on the branches and leaves of trees and plants. When these eggs hatch, the larvae, which are the inchworms you often encounter, emerge.

These inchworms have a peculiar method of locomotion, which involves looping their bodies into a shape resembling the letter “U.” As they progress through their life cycle, the inchworms will eventually transform into adult moths, completing their journey and allowing the cycle to continue.

Understanding Inchworms

Characteristics of Inchworms

Inchworms, also known as loopers or measuring worms, are caterpillars from the family Geometridae, which falls under the order Lepidoptera. An inchworm’s body is color, smooth, cylindrical, and hairless, allowing it to effectively camouflage itself in various environments. The distinguishing feature of inchworms, as opposed to other caterpillars, is their unique “looping” motion when they move around.

Some key features of inchworms include:

  • Unique looping movement
  • Caterpillar stage in the geometridae family
  • Effective camouflage thanks to their smooth, cylindrical and hairless body

Different Species of Inchworms

There are more than 1,400 species of inchworms across North America, and they feed on a wide range of deciduous trees, shrubs, and ornamentals. Some notable species of inchworms are:

  • Cankerworms: Cankerworms can cause significant defoliation of various deciduous landscape and forest trees during large outbreaks.
  • Spring and Fall Cankerworms: These inchworm species differ in their number of prolegs (false legs) on their abdomens and the time they’re active, with one peaking in the spring while the other is active in the fall.
  • Spanworms: Spanworms may specifically target conifers, while others focus on deciduous trees and shrubs.
Species Prefered Host Appearance
Cankerworms Deciduous trees Varies, but generally cylindrical and hairless
Spring Cankerworm Deciduous trees Maybe yellow-green to brownish to blackish with a white stripe on the side
Fall Cankerworm Deciduous trees Can range from light green to dark green to black
Spanworms Conifers or Deciduous These may vary depending on the specific species within the spanworm group

You may come across various species of inchworms depending on your location and the type of vegetation in your area. By understanding their characteristics and preferred host plants, you’ll be better equipped to identify and manage these fascinating caterpillars.

Life Cycle of Inchworms

From Egg to Larvae

Inchworms, also known as cankerworms, start their life cycle as eggs. Adult moths lay their eggs on the branches and leaves of trees. When the eggs hatch, tiny larvae emerge. These larvae have a unique appearance with fewer prolegs than other caterpillars, which results in their distinctive “looping” movement.

Some characteristics of inchworm larvae:

  • Yellow-green, brownish, or blackish color
  • A white stripe may run along the side of the body
  • Feed on a variety of trees and shrubs

Pupal Stage

After a period of feeding and growing, the inchworm larvae enter the pupal stage. They transform into pupae, encased in protective cocoons. This stage is crucial for their growth and development into adult moths. During this time, they undergo a process called metamorphosis that changes their bodies into a completely new form.

Key features of the pupal stage:

  • Encased in protective cocoons
  • Undergo metamorphosis

The Adult Moth

Once the pupal stage is complete, the transformed inchworm emerges as an adult geometer moth. Adult moths have fully developed wings, allowing them to fly and reproduce. They typically have a short life span and do not feed during this stage. Their primary goal is to mate and lay eggs, continuing the life cycle.

Features of adult geometer moths:

  • Fully developed wings
  • Short life span
  • Do not feed in this stage

Remember, it is important to familiarize yourself with the life cycle of inchworms as understanding their phases can assist you in dealing with them in your garden or landscape effectively.

Habitat and Diet of Inchworms

Inchworms, also known as measuring worms or spanworms, are a part of the geometer moth family. They can be found in various habitats, feasting on different types of plants.

You can observe inchworms on several trees like oak, maple, and mulberry. They fancy fruit trees as well, and bushes in your garden aren’t safe either. Inchworms enjoy nibbling on garden plants, leaves, and twigs, making them a nuisance for many gardeners. They may also be drawn to your vegetable garden.

These little creatures have diverse food preferences, depending on their species. For example, some inchworms specifically target conifers, while others prefer feasting on deciduous trees. Certain species may even feed on flowers or invade your blueberry bushes.

Here’s a comparison table to help you understand inchworms’ habitat preferences:

Habitat Food Source Example
Trees Leaves & twigs Oak, maple
Fruit Trees Leaves & fruits Mulberry
Bushes Leaves Garden bushes
Garden Plants Leaves & flowers Vegetable garden
Conifers Leaves & needles Pine tree
Deciduous Trees Leaves Birch tree

Remember to keep a close eye on your plants and trees to spot any signs of inchworms. Staying informed about their habitat and diet will help you address an infestation if it occurs in your garden.

Understanding the Unique Movement of Inchworms

Looping Motion

Inchworms, also known as loopers, move in a distinctive looping motion. This movement is due to their unique body structure, which includes both legs and prolegs. Let’s take a closer look at how these tiny creatures achieve their fascinating motion.

To begin, inchworms have two main types of legs: the true legs at the front and the prolegs at the rear. As they move, the inchworm first extends its body fully, using its true legs to anchor onto the surface. Next, it contracts its body, bringing the prolegs closer to the true legs. This establishes the “loop” shape that gives them their name.

Here are some key features of inchworm movement:

  • Distinct looping motion
  • True legs and prolegs work together
  • Body contracts and extends in a coordinated manner

A comparison of the different leg types involved in inchworm movement:

Type of Legs Location on Body Role in Movement
True Legs Front Anchor onto surface
Prolegs Rear Help create loop shape

So, the next time you observe one of these fascinating little creatures, you can appreciate the unique interaction between the inchworm’s legs and prolegs that creates its signature looping motion.

Inchworms as Pests

Inchworms in Garden Plants

Inchworms, also known as cankerworms, can cause damage to various plants in your garden. These pests feed on ornamentals like rhododendron, native trees, and shrubs. Their feeding habits may result in:

  • Defoliation of trees and shrubs
  • Stress to the plants
  • Decreased crop yields

The infestation can especially impact your vegetable garden, leaving you with less produce to harvest.

Methods of Control

Controlling inchworms is crucial to maintain a healthy garden. Here are some methods to consider:

  • Bacillus thuringiensis (Bt): This non-toxic bacteria specifically targets inchworms, leaving other beneficial insects unharmed. Bt can be easily applied to your plants as a spray.
  • Trichogramma wasps: Introducing these beneficial insects in your garden helps control inchworm populations. The wasps are parasitic and lay their eggs inside inchworm eggs, helping reduce future generations.
  • Chemical pesticides: In cases of severe infestation, using chemical pesticides may be necessary. However, they should be used cautiously, as they can harm beneficial insects and the environment.

Keep in mind that combining these methods can lead to better results in controlling inchworms and maintaining a healthy garden.

Here’s a comparison table for your reference:

Control Method Pros Cons
Bacillus thuringiensis Non-toxic, targets inchworms May need repeated applications
Trichogramma wasps Targets inchworms, reduces population May take time to establish in the garden
Chemical pesticides Effective in severe infestations Can harm beneficial insects and the environment

To manage inchworm infestations, use these methods wisely. With proper control strategies, you can safeguard your garden plants and ensure they remain healthy and stress-free.

Natural Predators of Inchworms

Birds and Spiders

In nature, inchworms face various predators, such as birds and spiders. Birds, including songbirds and woodpeckers, feed on inchworms as a nutritious meal. On the other side, spiders sit and wait to ambush these wriggly creatures in their webs.

You might notice that inchworm populations fluctuate depending on the presence of these predators in your garden. They play a critical role in controlling inchworm population.

Other Insect Predators

Inchworms also fall prey to several carnivorous insects. Some of the significant ones are:

  • Yellow jackets: These wasps are prominent predators of inchworms, attacking and feeding on them.
  • Paper wasps: Similar to yellow jackets, they hunt for inchworms as part of their diet.
  • Sawfly larvae: These insects consume inchworms and sometimes compete with them for food resources.
  • Earwigs: They prey on various insects, including inchworms, which they consume to supplement their diet.

Here’s a comparative table of the predators:

Predator Hunting method Impact on inchworm population
Birds Active hunters, catch inchworms by sight and movement Significant
Spiders Passive hunters, ambush inchworms in webs Moderate
Yellow Jackets Active hunters, attack and feed on inchworms Moderate
Paper Wasps Active hunters, feed on inchworms Moderate
Sawfly larvae Competition for food resources, consume inchworms Low
Earwigs Generalist predators, consume inchworms as supplement Low

Remember that a balanced ecosystem with these natural predators is essential in controlling inchworm populations and maintaining a healthy environment for your garden.

Additional Information on Inchworms

Inchworms are fascinating creatures that can be observed during different seasons, such as spring and fall. These caterpillars are known for their unique “looping” motion as they move. Here is some additional information to help understand them better.

Activities and Behavior

While some inchworm species are active during the day, others are nocturnal and prefer to go about their business at night. This can vary depending on the specific species. They have a fascinating defense mechanism: when threatened, they stand straight, blending in with the environment to resemble a twig.

Physical Features

Inchworms have a distinctive body structure. They possess only two or three pairs of true legs at the front and a few pairs of prolegs at the back, causing their looping movement. The colors of spring and fall cankerworms, a type of inchworm, can vary from yellow-green, brownish, and blackish, with many sporting a white stripe running the length of their bodies.

Lifecycle and Environment

During their life cycle, inchworms produce silk, which they use to pupate. Once they metamorphose into moths, their wingspans vary based on the species. They lay their eggs on trees and plants, which offer sustenance to the growing caterpillars.

Examples of inchworm habitats:

  • Ornamental plants, such as rhododendron
  • Coniferous trees
  • Deciduous trees and shrubs

In conclusion, inchworms play a critical role in the ecosystem. It’s essential to learn more about these fascinating critters to promote their conservation and understanding.


  • Bugman

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

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  • 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.

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8 thoughts on “Where Do Inchworms Come From? Unraveling Nature’s Tiny Secret”

  1. Thanks for the prompt reply! Yes, Chlorophyta: C. comosum and (I think) C. bichetii… they are the only plants on attacked. This has been a recurrent problem – year on year around this time -however it was only recently that I managed to track these guys down. Brilliant camouflage – they have been hiding in plain sight by standing as straight and rigid as twigs, maintaining the guise even when handled. While I allow other caterpillars to munch away, these guys are way too destructive as they basically cut across the central vein of the leaf for the smaller bichetii, causing it to fall off and die vs. just making holes. Necessary carnage, sorry!

  2. My son’s bed between the sheets not on the blankets had possibly a 100 or so of these. We have checked the cat and other areas of the house. He always makes his bed and we have no idea what they are or where they would have come from. I would have taken a picture but I quickly rolled up the sheets and bleached them in hot bleach water. Help! Where would they have come from? We live in northern Indiana.

  3. Hello. I found something that looks like this little black inch worm on top of my washing machine. found 2, then few days later found 9 crawling on top of the washer where I add bleach. Would those be inch worms as well? Scoured the internet and this is pretty much what they look like

  4. This worm was abut an inch long brown in colour, and moved by pushing its head forward then pushing lts rear part forward making a loop in its middle. When touched it coiled it’s self into a Cumberland sausage shape. At 71 years fished all my life never seen one before. This was on my bathroom floor

  5. I had stopped visiting your site during the hiatus, but just hit the button for it by mistake a minute ago. I’m more than delighted you’re back and want to take the occasion to thank you for your efforts over the years. As with so many of life’s good things, you don’t fully appreciate them until they’re gone and you appreciate ’em even more when they come back.

    • Thanks for your kind words Jim. Daniel cannot even begin to contemplate the backlog of identification requests and comments that arrived in the past year, and on slow days he can try to mine identification requests for gems, but for now, all Daniel can hope for is to move forward and to try to remain current and to try to concentrate on quality as opposed to the quantity of postings.


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