Do inchworms sleep? Unveiling the mystery of their rest habits

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Inchworms, also known as measuring worms or spanworms, belong to a family of moths called geometers. These tiny critters are often found on ornamentals, native trees, and shrubs, with some species feeding exclusively on conifers and others on deciduous trees and shrubs (source).

Many people wonder if inchworms sleep, as their routines and habits remain rather elusive. To understand if inchworms sleep or not, it’s essential to consider how they survive and thrive in their natural environment. While there is no definitive consensus on inchworms sleeping patterns, their behavior might reveal some clues.

Most inchworms are active during the day, moving, and feeding mainly on leaves. These tiny creatures may have periods of rest or inactivity during their daily routine, but it’s unclear if these breaks are considered sleep. Further research is needed to fully understand if inchworms have a defined sleep cycle like other animals or insects.

Inchworm Basics

Appearance and Size

Inchworms are small, soft-bodied, and have a distinct shape due to their unique leg arrangement. They have three pairs of legs at the front and two pairs of legs at the back, with no legs in the middle. This results in their characteristic “looping” movement. Inchworms come in various colors, depending on the species, including shades of green, brown, and gray.

Typically, the size of inchworms ranges from 0.4 to 1 inch (10 to 25 mm) in length. One example is the common inchworm, which feeds on a wide range of plants.

Habitat and Distribution

Inchworms belong to a family of moths called geometers. They inhabit various environments, such as forests, gardens, and grasslands, depending on the species. Their distribution is widespread, with some species being exclusive to a specific habitat, such as coniferous or deciduous trees, whereas others can be found in multiple habitats.

Here are some key characteristics of inchworms:

  • Soft-bodied and various colors.
  • Unique leg arrangement and looping movement.
  • Widespread distribution and species-specific habitats.

Some examples of different inchworm species and their habitats:

  • Conifer-feeding inchworms: These species are found in coniferous forests.
  • Deciduous tree-feeding inchworms: These species are mainly found in deciduous forest environments.
  • Generalist inchworms: These species can be found in gardens, grasslands, and other mixed habitats.

Inchworm Life Cycle

Eggs and Larvae

Inchworms start their life as eggs. The female adult moth lays these eggs, usually in spring. After hatching, the larvae emerge, and we commonly know them as inchworms or cankerworms. These small caterpillars have a distinct looping motion as they move around the deciduous landscape or forest trees 1.

Some features of inchworm eggs and larvae include:

  • Female adult moths lay eggs in spring
  • Eggs hatch into larvae (also known as inchworms or cankerworms)
  • Larvae move with a unique looping motion


Once the inchworms complete their feeding phase, usually within 3-4 weeks, they transform into the pupa stage 2. At this stage, the larvae either crawl or drop to the ground using silken threads and pupate in the soil.

Characteristics of the pupa stage:

  • Transition from larvae to adult moths
  • Inchworms pupate in the soil
  • Lasts for a variable amount of time

Adult Moths

After the pupa stage, adult moths emerge, and the life cycle continues 2. These adult moths vary in appearance, with wingless females crawling up tree trunks to lay eggs and mate with winged males.

Pros and cons of the inchworm life cycle include:


  • Contribute to the ecosystem as food for different animals
  • Some inchworm species help control harmful plant pests


  • Large outbreaks of inchworms can cause significant defoliation on trees
  • Certain species considered pests in agricultural settings

Here’s a comparison table elucidating the different stages of the inchworm life cycle:

Stage Key Features Duration
Eggs Laid by female moths Spring
Larvae Inchworms, distinct looping movement 3-4 weeks
Pupa Transition from larvae to moth, pupate in the soil Variable
Adult Moth Wingless females and winged males, reproduce Until next cycle

Feeding Habits and Diet

Preferred Food Sources

Inchworms, also known as caterpillars, are herbivores that primarily feed on the leaves of various plants. Some examples include:

  • Deciduous trees
  • Coniferous trees
  • Shrubs
  • Blueberry plants

They tend to prefer the foliage of trees and shrubs1, especially those with tender, new growth.

Nocturnal Eating Habits

Inchworms are mostly nocturnal eaters, meaning they feed during nighttime. This aids in avoiding predators2. Here is a comparison of their nocturnal and diurnal (daytime) habits:

Activity Nocturnal (Night) Diurnal (Day)
Feeding Yes Rare
Rest/Digest No Yes

Their nocturnal eating habits allow inchworms to consume a significant amount of leaves and plants during the night, while they rest and digest during the day.

Overall, inchworms play a significant role in the ecosystem, serving as a food source for other organisms and contributing to plant growth.

Inchworm and Plant Interaction

Infestation and Damage

Inchworms, also known as measuring worms or spanworms, belong to a family of moths called geometers. They feed on various plants, including ornamentals and native trees and shrubs. Infestations can occur on numerous plant species, with some inchworms specifically infesting conifers, while others target deciduous trees and shrubs.

Some examples of trees inchworms can infest are:

  • Maple
  • Oak
  • Birch
  • Pine

Damage caused by these pests can vary from minor leaf damage to severe defoliation if the infestation is left unchecked.

Plant Defense Mechanisms

Plants have developed various defense mechanisms against herbivorous insects like inchworms. These include:

  • Production of toxins
  • Creation of defensive proteins

These mechanisms target the physiological processes in the insect, hindering its growth and reproduction. Additionally, plants may release chemical signals that attract predators of the pests, leading to a reduction in the infestation.

Table 1: Comparing strategies used by inchworms and plants

Inchworm Strategy Plant Defense
Feeding on leaves Producing toxins
Targeting specific species Developing defensive proteins
Continuous feeding Attracting predators via chemical signals

Overall, it is crucial to monitor and manage inchworm infestations in gardens and forests, as their impact on plant life can be significant if uncontrolled. Plant defense mechanisms play a vital role in nature’s balance, providing an essential line of resistance against herbivorous pests like inchworms.

Predators and Threats

Common Predators

Inchworms face various predators in their environment, including:

  • Birds: Many bird species feed on inchworms as a protein source.
  • Spiders: They prey on inchworms by trapping them in their webs or through active hunting.
  • Carnivorous insects: Some species, such as ladybugs and predatory wasps, also eat inchworms.
Predator Hunting Strategy
Birds Visual detection, followed by pecking
Spiders Using webs or active hunting
Carnivorous insects Scouting and capturing small insects

Defensive Strategies

Inchworms have developed various defense mechanisms to evade predators:

  1. Camouflage: They blend in with their surroundings, often resembling twigs or plant stems.
  2. Eyespots: Some inchworm species possess eyespots on their bodies, giving the illusion of a larger, more threatening creature.

In conclusion, inchworms employ both camouflage and eyespots to help protect themselves from predators like birds, spiders, and carnivorous insects. By understanding their predators’ hunting strategies, inchworms have adapted various defensive techniques to increase their chances of survival.

Pest Control Methods

Natural Predators and Pests

Inchworms can be managed with their natural predators:

  • Birds
  • Predatory insects

For example, ladybugs act as a natural enemy to inchworms and other pest insects.

Chemical Pest Control

Chemical control methods include the use of synthetic pesticides and insecticides:


  • Fast-acting
  • Effective against many pests


  • Harmful to beneficial insects
  • Potential environmental impact
  • Risk of pest resistance

Bacillus thuringiensis (Bt) offers a more specific control, targeting only caterpillar pests like inchworms with less harmful side-effects.

Organic Pest Control

Organic control options provide a more environmentally friendly solution, such as:

  • Neem oil
  • Diatomaceous earth
  • Insecticidal soap
Method Pros Cons
Chemical Pest Control Fast-acting, effective against many pests Harmful to beneficial insects, potential environmental impact, risk of pest resistance
Organic Pest Control Environmentally friendly, safer for beneficial insects May require more frequent applications, sometimes less effective than chemical options

An example of successful organic control is Bacillus thuringiensis, a naturally occurring bacterium that acts as a toxin for caterpillar pests like inchworms.

Interesting Inchworm Facts

Unique Locomotion

Inchworms, also known as loopers, measuring worms, or spanworms, have a distinct crawling pattern due to the absence of legs in their middle body section. They move by:

  • Extending the front part of their body
  • Bringing the back part closer
  • Forming a “loop” shape

These fascinating creatures can travel faster than expected for their small size.

Role in Ecosystem

Inchworms play a vital role in their ecosystem as they:

  • Consume leaves from various plants, aiding in natural pruning
  • Provide a food source for many predators, such as birds and spiders

They are often found on ornamentals, native trees, and shrubs, contributing to the balance and diversity of their environment.

Do Inchworms Sleep?

Inchworms, like many insects, do not sleep in the same sense as humans. They experience periods of rest but are not known to enter a deep sleep state. The resting activity of inchworms can be observed:

  • During the day, when they are less active
  • At night, when they crawl back towards leaves to hide and seek protection

Inchworms usually do not go underground to rest. Their lifespan is relatively short, typically a few weeks as caterpillars and up to a month as adult moths, making efficient use of their time for feeding and reproduction.

Here is a comparison of inchworms and their nocturnal activities:

Features Inchworms
Sleep No deep sleep, periods of rest
Day Less active
Night Hide in leaves
Location Above ground
Lifespan Short-lived, weeks to a month


Inchworms, also known as measuring worms, belong to a family of moths called geometers. These insects consume a variety of plants, including ornamentals and native trees, depending on the species.

Regarding their sleep patterns, research in sleep among a variety of creatures focuses primarily on vertebrates. However, sleep-like states can be observed in invertebrates like insects, although their activity patterns may differ significantly from those of vertebrates. As such, determining whether inchworms sleep cannot be definitively answered with currently available information.

Here’s a brief comparison of inchworms to other organisms to provide context:

Organism Sleep? Additional Information
Inchworm Uncertain Insect, needs more research
Humans Yes REM and NREM sleep
Fish Yes (varies by species) Sleep with open eyes

It is crucial to consider the diverse characteristics and behaviors of various species when discussing sleep patterns. Further research is required to better understand the sleep behavior of inchworms and other invertebrates.


  1. University of Kentucky – Cankerworms 2

  2. Texas A&M University – Cankerworms and inchworms 2 3

Reader Emails

Over the years, our website, 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 – Inchworm


Unknown Caterpillar
Location: Sarasota, Florida. (South West Florida)
March 30, 2011 1:10 pm
I was looking through some of my books on caterpillars but couldn’t find this one and also looked on your site but also didn’t come across it and would like to know what it is! It’s a brown/grey color with red spots along the sides. Found it in my backyard. Wasn’t on a plant, but when you pick it up it goes straight like a stick. Found it on 3/30/2011; Afternoon; Currently Humid and windy.
Signature: Shelby


Hi Shelby,
Your caterpillar is in the family Geometridae, and it is commonly called an Inchworm, Spanworm or Measuringworm because of its unusual manner of locomotion.  It crawls forward on its six true legs and the loops the rear portion of its body forward with its two pairs of prolegs.  Inchworms are also called Loopers.  Most caterpillars have five pairs of prolegs, but Inchworms have only two which necessitates this unusual manner of locomotion.  We will try to identify your species if we have time by browsing the hundreds of possibilities on BugGuide.  Interestingly, we decided in the past few days that the featured Bug of the Month for April 2011 is the Inchworm, so your identification request is quite timely.

Letter 2 – Horned Spanworm Moth


filament bearer caterpillar
Sat, Oct 18, 2008 at 9:22 AM
Hi Buggies,
I love your website. I searched for this species of caterpillar, but couldn’t find it on your site–thought you might like to see this filament bearer, Nemocampa resistaria (according to my Caterpillars of Eastern North America by David L. Wagner, a book no Eastern North American bug lover should be without). I took this photo in my back yard in northwestern New Jersey in early June of 2008. When I saw the caterpillar inching across the picnic table, my first thought was, “There’s no breeze; why is that twig moving?” It does look just like a piece of Virginia Creeper vine, or the wild grape vines that also grow around here.
Newton, New Jersey

Horned Spanworm
Horned Spanworm

Hi Jeannie,
BugGuide also refers to this interesting inchworm species as the Horned Spanworm.  Your wonderful photo with its dramatic shadow is a perfect Halloween image.

Letter 3 – Horned Spanworm


Location: East Tennessee, Great Smoky Mountains National Park
May 24, 2011 8:24 pm
I found this oddball on my shirt after walking through some trees ( mostly ironwood, sweetgum, red maple, but there were other around) near a river in Great Smoky Mountains National Park in TN – about elevation 1500’. Sorry just one picture! I couldn’t find anything like it in David Wagner’s excellent Caterpillar field guide…
Signature: John D.

Horned Spanworm

Dear John,
Most caterpillars have five pairs of prolegs at the anterior end of the body and these prolegs assist in the caterpillar locomotion.  Many caterpillars in the family Geometridae have only two pairs of prolegs, so their method of locomotion is unusual.  They crawl forward on their true legs and then loop the rear portion of the body forward.  Because of this manner of locomotion, they are commonly called Inchworms or Spanworms.  The filaments on your specimen are very unusual and immediately indicate it is a member of the genus
Nematocampa, most likely the Horned Spanworm, Nematocampa resistaria, which we identified on BugGuide.  According to BugGuide:  “Larvae feed on many hardwoods and several softwood species of shrubs and trees including pine, hemlock, fir, larch and spruce.”

Letter 4 – Inchworm


Need ID on this caterpillar
Found this caterpillar on my sages and coyote mints eats leafs and builds nest at base of plants. About 1/2″ long. Located in Southern California
Second picture is another caterpillar I found in my backyard
Brea California


Hi Dennis,
One of the caterpillars is and Inchworm or Spanworm in the family Geometridae.  We are not sure of the exact species as there are numerous similar looking caterpillars posted to BugGuide.  We have a similar looking caterpillar that defoliates the new growth on our Matilija Poppy each spring.

Letter 5 – Filament Bearer


Subject: Bug identification
Location: Bowling Green, Ohio USA
May 24, 2015 2:47 pm
I found this bug crawling on my shoulder and have never seen one that looks like this. I live in Bowling Green, Ohio and was curious what it is. I heard about a kind of caterpillar that will bite and leave welts. I have children and want to make sure this bug is not harmful. Thank you so much in advance.
Signature: Stephanie P

Filament Bearer
Filament Bearer

Dear Stephanie,
This Inchworm in the family Geometridae is a Filament Bearer or Horned Spanworm in the genus
Nematocampa which you can verify on BugGuide.  In our opinion, this is not a harmful species.

Thank you so much for the speedy answer! I feel a lot better now that I know what it is and that it is harmless! Stephanie

Letter 6 – Filament Bearer


Subject: Caterpillar/Inchworm Michigan
Location: Redford, Michigan
May 31, 2016 6:40 am
Dear Bugman,
This little caterpillar fell on my arm, while I was sitting under a Black Walnut Tree in southeastern Michigan on 5/28/2016. He was quite small, maybe inch long and a quarter inch wide.
Thank you for the service you provide.
Signature: Kristin

Filament Bearer
Filament Bearer

Dear Kristin,
This Inchworm is one of the Filament Bearers in the genus
Nematocampa, an identification that can be verified on BugGuide.

Letter 7 – Horned Spanworm


Horned Spanworm
April 18, 2010
Thanks for all the help you’ve given me! But here’s one I found myself that I’d like to share: a horned spanworm (OK, I’m pretty sure that’s what it is). I found it lurking on a maple seedling, and from what I’ve read, was probably responsible for the chew marks on several of the maple leaves (primary habitat is deciduous and coniferous trees). It is interesting to note that between the first picture and the latter pictures, the ‘tentacles’ continued extending (must be camera shy). I found the textured orange patch on his upper back very interesting; I saw it on few of the other photos I viewed. Also, it was very reluctant to uncurl.
Karen H.
Belleview, FL

Horned Spanworm

Hi Karen,
Thank you so much for submitting your images of a Horned Spanworm, Nematocampa resistaria.

Horned Spanworm


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    Bugman aka Daniel Marlos has been identifying bugs since 1999. 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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6 Comments. Leave new

  • Two pair of abdominal prolegs says Looper in the Plusiinae, maybe Cabbage Looper, Wagner page 377

  • Amy Cunningham
    June 21, 2015 8:36 am

    Is it poisonous? I found one on my front porch and I have a cat that likes to sit on the porch. Please let me know thank you.

  • we get a bug in our house that looks like an inchworm .we have cement floors a very old house and it seems like when it rains i find these bugs crawling in my house they are an inch long have many legs and somewhat of a hard body they are a dark color and i need to know what i can do about them. thank you Donna

  • Cabbage looper moth (they are semi loopers. Polyphageous so eat a variety of plants. Geometridae only have two pairs of prolegs I think.


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