Inchworm: All You Need to Know for a Fascinating Discovery

folder_openInsecta, Lepidoptera
comment2 Comments

Inchworms, also known as measuring worms or spanworms, are the larval stage of moths belonging to the family Geometridae. They are known for their distinctive looping movement and are found in various species that feed on an array of plants, including ornamentals like rhododendron, as well as native trees and shrubs source.

These small caterpillars can range in color from yellow-green to brownish to blackish, depending on the particular species source. Some inchworms feed exclusively on conifers, while others only feed on deciduous trees and shrubs. Despite their small size, inchworms can cause significant damage to plants due to their voracious appetite.

Inchworm Basics

Appearance

Inchworms are small caterpillars that belong to the family Geometridae. They have a distinct crawling locomotion, forming a loop with their body as they move1. Their color varies, with some being yellow-green, brownish, blackish, or even with white stripes running along their sides2.

Variations and Species

There are many different species of inchworms, including cankerworms and loopers3. They belong to the geometer moth family and feed on a variety of plants, such as ornamentals, conifers, and deciduous trees4. Some inchworms feed exclusively on specific tree types5.

Habitat

Inchworms can be found in various environments where their host plants are present. These caterpillars thrive in forests, gardens, and urban landscapes6.

Lifespan

The lifespan of inchworms varies by species, but they generally complete their life cycle in a matter of weeks7.

Comparison Table:

Inchworm Type Color Host Plant
Cankerworms Yellow-green Deciduous trees
  Brownish  
  Blackish  
  White stripe  
Loopers Light to dark Conifers
  Green  
  Black  

Inchworm Characteristics:

  • Small caterpillars
  • Distinct loop-forming locomotion
  • Belong to family Geometridae
  • Vary in color and host plant preferences

Inchworm Lifecycle

Caterpillar Stage

Inchworms, also known as measuring worms or spanworms, are the caterpillar stage of moths from the geometer family1. They are typically found feeding on leaves of various plants, including ornamentals, native trees, and shrubs2. Their movement is characterized by forming a loop as they crawl, resembling a measuring process3. Inchworms’ diet mainly consists of leaves, making them potential pests to gardens and plants. Some species exclusively feed on conifers, while others prefer deciduous trees and shrubs2.

Cocoon Stage

After their growth as caterpillars, inchworms enter the cocoon stage, where they use silk to create protective coverings for their transformation. During this time, they remain inactive and focus on their metamorphosis into moths. The cocoon helps protect them from external threats like predators and unfavorable weather conditions.

Moth Stage

Once the metamorphosis is complete, adult moths emerge from the cocoon. These moths can vary in appearance, from the spring cankerworms’ yellow-green to brownish colors, sometimes featuring a white stripe along the body4, to the fall cankerworms that range from light green to dark green to black4. Moths play an essential role in the ecosystem as both pollinators and food sources for other organisms, such as birds and mice.

Characteristics of Inchworm Lifecycle:

  • Caterpillar stage: feed on leaves, potential pests to plants
  • Cocoon stage: create silk coverings, metamorphosis occurs
  • Moth stage: emerge as adult moths, serve as pollinators and food sources

Comparison between Spring Cankerworms and Fall Cankerworms:

  Spring Cankerworms Fall Cankerworms
Color Yellow-green to brownish Light green to dark green to black
Markings May have a white stripe along the body None mentioned

Inchworms in Nature

Plant Damage and Infestation

Inchworms, also known as measuring worms or spanworms, feed on a variety of plants, including:

  • Oak
  • Fruit trees (e.g., apple, mulberry)
  • Vegetable garden plants

These caterpillars can cause leaf damage and defoliation, especially during large outbreaks.

Inchworms as Food Source for Predators

Inchworms are an important food source for many predators, such as:

  • Birds
  • Small mammals
  • Other insects

This natural predation helps to control inchworm populations and protect plants from severe infestations.

Inchworm Pest Control

Signs of Infestation

Inchworms, also known as spring and fall cankerworms, are small caterpillars that can cause damage to leaves on trees like firs, oaks, elms, and lindens. Signs of infestation include:

  • Chewed or skeletonized leaves
  • Small, poop-like droppings on leaves or ground
  • Sightings of inchworms on leaves or tree trunks

Natural Pest Control Methods

There are several eco-friendly ways to manage inchworm infestations:

Stress-Free Trees

  • Keep trees healthy with proper pruning and watering.

Beneficial Insects

  • Attract natural predators like ladybugs, lacewings, and parasitic wasps.

Bacillus Thuringiensis (BT)

  • BT is a bacteria that specifically targets inchworms.
  • Apply BT to leaves for a highly effective, non-toxic control method.

Chemical Pest Control Methods

When natural methods aren’t enough, consider using chemical pesticides:

Insecticides

  • Choose a product labeled for use on inchworms.
  • Apply according to labeled instructions.

Pros:

  • Quick results
  • Effective even in severe infestations

Cons:

  • May kill beneficial insects
  • Potential environmental and health concerns
Method Eco-Friendly Targeted to Inchworms Cons
Stress-Free Trees Yes No
Beneficial Insects Yes Yes May take time to work
Bacillus Thuringiensis Yes Yes Need to reapply
Insecticides No Yes Harms beneficial insects

Bug Control Recommendation Tool

What type of pest are you dealing with?

How severe is the infestation?

Do you require child/pet/garden safe treatments (organic)?

Are you willing to monitor and maintain the treatment yourself?


Inchworm Exercise

Benefits and Muscles Worked

The Inchworm exercise is a full-body workout that targets several muscle groups, particularly:

  • Core: Engages the abs and lower back
  • Upper body: Works the chest, shoulders, and arms
  • Lower body: Strengthens the hamstrings, glutes, and calves

In addition to building strength, the Inchworm exercise is also effective in improving posture and flexibility. It can be incorporated into strength training routines or high-intensity interval training (HIIT) for a dynamic, full-body challenge.

Proper Form and Technique

  1. Stand with feet hip-width apart
  2. Bend at the waist, keep legs straight, and touch the ground
  3. Walk hands forward into a high plank position
  4. Walk feet up towards hands, maintain a straight back
  5. Repeat for desired number of reps

Remember to maintain a steady breath throughout the exercise and engage the core in each position.

Common Mistakes and How to Avoid Them

  • Arching the lower back: Engage the core to maintain a straight back in both plank and standing positions
  • Bending the neck: Keep the neck aligned with the spine to avoid strain
  • Rushing through reps: Maintain a controlled speed to ensure proper form and to get the most out of the exercise

Variations and Modifications

  • Beginner: Perform the Inchworm with knees bent in the standing position and modified plank on the knees
  • Advanced: Add a push-up in the high plank position for an additional upper-body challenge
  • With dumbbells: Add dumbbells to the plank position for increased resistance and intensity

Footnotes

  1. Utah State University 2
  2. University of Minnesota Extension 2 3
  3. Texas A&M University 2
  4. Washington State University 2 3
  5. Washington State University
  6. University of Minnesota Extension
  7. Utah State University

Reader Emails

Over the years, our website, whatsthatbug.com 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 – Bug of the Month April 2011: Inchworm

 

Looper
Location: Fairfield, California
March 28, 2011 7:09 pm
Hi,
Every spring and summer I find these in our garden and would love to know what type of insect it is. Most recent find was on 3-26-11 on a Japanese maple, but I have found them on Lantana and also just hanging out on on the fence. I never see any feeding damage on the plants the looper is on. Thanks!
Signature: Sharon

Inchworm

Dear Sharon,
At the moment, we are only going to be able to provide you with a very general Family identification, which you may already know.  This is an Inchworm or Spanworm or Measuringworm in the family Geometridae, and browsing through BugGuide will reveal many similar looking caterpillars.  Inchworms are also sometimes called Loopers, though not all Loopers are in the family Geometridae.  The Inchworm gets its common name because of its manner of locomotion, which your photo beautifully illustrates.  Most caterpillars have five pairs of prolegs, but Inchworms have only two pairs, which results in the caterpillar walking forward with the fore part of the body in a typical manner, and then looping the rear portion of the body to catch up, causing the larva to appear as though it is measuring distance as it moves.  Your second photo demonstrates the marvelous camouflage ability these caterpillars have for mimicking small twigs.  We are not certain what species of Inchworm you have submitted, but we suspect the species found on the Lantana might be different from the individual you found on the maple.  Many Inchworms look very similar and they are difficult to distinguish from other members of the family.  Since it is the end of March, it is time for us to select a Bug of the Month for April, and we love your photos so much, we have decided to give your Inchworm that honor.  With the dormant trees beginning to produce tender leaves in many parts of the country, young caterpillars will start appearing as well to feed on those leaves.  The vast majority of our caterpillar submissions occur in the fall when large fully developed Caterpillars leave their host plants to find places to pupate, but sharp eyed observers will be able to find Caterpillars in the spring as well.

Hi Daniel!
I am absolutely thrilled (can’t stop smiling) that you have chosen my submission as worthy for BOM! I am a “wannabe” entomologist, to the point that I lead the introduction to entomology for my county’s Master Gardener training class. I am a certified Master Gardener and photography is another of my hobbies. I hope to culture this inchworm through to its adult stage (to help in the identification). I have tried before, but my captive conditions do not seem suitable for success. Perhaps a larger terrarium with native soil will help.
And thank you for the lesson on inchworm definition (vs. caterpillar), I will share this information with my Master Gardener peers and trainees! Thank you, again!
Cheers!
Sharon Leos

Letter 2 – Camouflaged Inchworm

 

15 Pages of Caterpillars… No Luck
Hey Bugman,
I searched your 15 pages of caterpillars frontwards, backwards and sideways trying to figure out who I captured on camera a couple of years ago in Peachtree, Georgia. Maybe this is something common that’s just in a different instar than a pic you have posted?  Whatever the case, I thought you might be interested.
Jim Olsson
Cheboygan, MI

Inchworm camouflaged with bits of plants
Inchworm camouflaged with bits of plants

Hi Jim,
We actually do have several images of Inchworms, the caterpillars of the Geometrid Moths, that have camouflaged themselves with plant material.  BugGuide has specimens from the genus Synchlora that exhibit this unusual behavior.  The appearance of the plant parts on your specimen is resulting in the appearance.  Other than the choice of plant material, there is one image on BugGuide that looks very much like your caterpillar.  Inchworms are also called Spanworms.

Letter 3 – Camouflaged Inchworm of Wavy-Lined Emerald Moth

 

camouflaged caterpiller
Hi,
This caterpillar was photographed in Atlanta, Georgia on Oct 8, 2004.
Several of these were on a blue mist flower. Their movement was very slow.
The length was less than 1/2 inch. They appeared to be eating the flower or
maybe just biting parts off to put on their bodies. I noticed their
movements while photographing bees and got a few shots of them.. I don’t
know what they are and haven’t been able to find any information on them in
field books or on the web.
I just found your website today and spent quite a while looking at all the
stuff. It’s one of the best bug sites I’ve seen.
Bill DuPree
Atlanta, Georgia

Thanks for the compliment Bill.
We were unsure as to an exact identification, so we turned to entomologist Eric Eaton who wrote back:
“Nice image! Wow! Yes, I have heard of this creature, it is an inchworm of some kind, family Geometridae. If I can dig up more information somewhere, then I will go ahead and send it along.”

Thanks Daniel,
I really apprecite your help. I sort of thought it might be an inchworm. Sometime when you’re not busy, check out my insect photo gallery on pbase. It’s insects and spiders mostly unidentified, especially the flies. Congrats on the Yahoo and the USA recognition!
Bill DuPree

Ed. Note: Several days later Bill wrote back:
Hope you remember the camouflaged inchworm photo. I may have an identification on it: wavy lined emerald moth (Synchlora aerata). Does that seem correct? Thanks,
Bill

Hi again Bill,
We did some web research with your new information and found a link with a photograph that looks like you are probably right. Thanks for the update.

Hi Daniel,
Thanks for the link. It does look similar. I just got a book by Thomas Eisner, “For Love of Insects”. The camo behavior is covered in chapter 8 and photos of Synchlora larva are shown both bare and in full dress. Evidently, several species of Synchlora larva camouflage themselves. I did a search for Synchlora to see how many species occurred in Georgia. I found at least 3 (there’s probably more), with the most common one being the wavy lined emerald moth. Most of the bugs I see are the common ones, so I’m guessing this one is too.
Boy, this bug ID business can get hard!
Bill

Letter 4 – Camouflaged Looper

 

Subject: Weirdest bug I’ve ever seen!
Location: Zebulon, NC
August 22, 2012 6:32 pm
This has to be the weirdest bug I’ve ever seen. There was more than one of them in my flower bed. I have so many different types of pollinators that at first I didn’t pay much attention to it. But upon closer inspection, I could see it was no ordinary bug.
I don’t know if it has some dead foliage on its back to act as camouflage, or if that’s its body, but the entire thing was moving on top of the flower. Can you help me out?
Signature: Melissa

Camouflaged Looper

Hi Melissa,
Though the camouflage element is obviously the dried petals of the flowers in your photo, the insect portion is not very visible in your otherwise lovely photograph.  We hope you have other angles of view to submit as well.  The most likely candidate is some type of caterpillar, probably a Camouflaged Looper,
Synchlora frondaria, but it is difficult to actually see the insect in your photo.  See some examples of photos of Camouflaged Loopers on BugGuide which states:  “A variable twig mimic. Larvae take on the colors of their host plant and employ decorative crypsis by attaching plant material to themselves.”   BugGuide also states:  “larval foodplants include sunflower, Bidens, Rudbeckia sp., and others” and the flower in your photograph is in the composite group that the Camouflaged Looper feeds upon.  The Camouflaged Looper will metamorphose into the Southern Emerald Moth.

That’s exactly what it is!  Thank you so much!  I’m attaching another photo I took this afternoon, from another angle.  I also got some video of it.  Fascinating creatures!

Camouflaged Looper

Thanks Melissa,
This image is a much better view of the insect known as the Camouflaged Looper.

Letter 5 – Camouflaged Looper

 

Subject: caterpillar wearing flower camoflage
Location: Auburn, NJ
September 9, 2012 8:57 am
Hi Bugman,
I took pics of a little inch worm type caterpillar a couple weeks ago, amazed I had never seen them before. I’ve taken dozens of pics of butterflies on these zinnas, but their camouflage is so effective, I mistook them as part of the flower. Luckily the camera lets me zoom in or I still might have missed them.
Over at bug guide came up with a close relative, but not sure the coloring is quite right to be a match: synchlora aerata? Am I getting close?
Thanks!
Signature: Creek Keeper

Camouflaged Looper

Hi there Creek Keeper,
You have correctly identified this Inchworm or Spanworm in the family Geometridae as the caterpillar of the Wavy-Lined Emerald,
Synchlora aerataAccording to BugGuide:  “Caterpillars feed on a wide variety of plants, often composite flowers but also many other flowering plants, shrubs and trees.”  The caterpillars use petals from flowers and other plant parts as a protective covering, hence the common name Camouflaged Looper.  BugGuide also states:  “Caterpillar adorns its body with plant fragments, usually flower petals, to camouflage it as it feeds. It is the only widespread species to do so(2), but from Maryland southwards other Synchlora spp. are also present and only raising to adulthood can yield a definite caterpillar ID.”  Since you are in New Jersey, we are relatively certain that the species identification is correct.

Camouflaged Looper

Ah,Daniel,  thanks so much!  I don’t know why I’m no longer seeing updates for your posts on Facebook, though I used to get them in news feed. If I had, I would have seen your previous posts and not been quite so lost looking for information.    I guess its the time line they changed me too?  But I just spent some time catching up.  Amazing things, bugs are.
thanks again,
Val

 

Letter 6 – Blackberry Looper from Canada

 

A compromised inchworm?
January 6, 2010
I found what I believe is an inchworm clinging to a blackberry leaf with her abdominal prolegs today, January 5.
The problem is, his/her head and thorax/legs are barely recognizable. The head area is almost split in two.
I found some skin on a leaf beside her. I wonder if a moulting process can look this horrible; either that, or could it be that the inchworm hasn’t fully developed? (The latter does not make sense to me, because I realize that insects typically hatch fully developed and simply grow/moult in the larval stage.)
This caterpillar was able to move just fine, as if otherwise healthy, but could only grab things with her prolegs… the head area is really looking bad!
Paul
Southwestern British Columbia, Canada

Unknown Inchworm
Blackberry Looper

Dear Paul,
We are not certain what species of Inchworm this is, and we haven’t the time to research it at the moment.  It is difficult to tell from your photographs if there is anything unusual with the physiognomy.  In the event there was trauma of some sort, a predator perhaps, we are uncertain how long a compromised caterpillar can continue to live.  Perhaps one of our readers has the time to research the species.

Unknown Inchworm
Blackberry Looper

Update
Immediately after posting, we tried to do a websearch of geometridae and blackberry, and we believe this is a Blackberry Looper, Chlorochlamys chloroleucaria, as pictured on BugGuide.  Though the coloration is different, the structure of the head is consistent with your photo.

Hello,
I did read the other emails, and I’m very glad for your answer!
I don’t know how to find it online.
Will need to visit your site more often!
Kind regards,
Paul

Authors

  • 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.

    View all posts
  • 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.

    View all posts
Tags: Inchworm

Related Posts

2 Comments. Leave new

  • Cyndy Holland
    May 22, 2016 11:37 pm

    I finally caught these interesting critters….
    There are demolishing our wonderful rose bushes. I don’t seem to be able to leave a photo here.

    Reply

Leave a Reply

Your email address will not be published. Required fields are marked *

Fill out this field
Fill out this field
Please enter a valid email address.
You need to agree with the terms to proceed

keyboard_arrow_up