Currently viewing the category: "Inchworms"
What's That Bug? does not endorse extermination

Subject: It moved!
Location: Slatington, PA
May 28, 2012 8:53 am
My mother found this thing outside of her house. She thought it was stick, and rightly so. And then it moved! EW! Please tell me what it is, I have never seen anything like this!
Signature: Mandy

Inchworm

Hi Mandy,
This is an Inchworm or Spanworm, the caterpillar of a moth in the family Geometridae.  They get their common name from the manner of locomotion.  As you can see in the photo where the Inchworm is up-side-down, there are three pairs of true legs near the head and only two pairs of false legs or prolegs near the posterior end of the body.  Most caterpillars have five pairs of prolegs and that enables them to move in an oscillating manner.  There is a drawing on the Enchanted Learning website that illustrates the anatomy of a typical caterpillar.  Inchworms need to crawl forward on their true legs and then loop the rear end of the body forward.  Many Inchworms are excellent twig mimics, and they are known to grasp a stem with the prolegs and stick the rest of the body straight out exactly like a twig.  Our Bug of the Month Posting for April 2011 was the Inchworm and the posting illustrates both the manner of locomotion and the twig mimic behavior.  

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Caterpillar
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.”

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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

Inchworm

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.

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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.

Inchworm camouflaged as twig

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

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Very abundant inch worm in Kasane, Botswana
Location: Kasane, Botswana
January 14, 2011 4:58 pm
I have seen this inch worm several times around my home in Kasane, Botswana. Right now it is the rainy season and is the only time I have seen this worm. It is very colorful and has almost feather like spikes. I did handle it and it was not poisonous. Do you know what this bug is or what it will become. It is very beautiful.
Signature: Laura Marchitto Massie

Unknown Caterpillar

Dear Laura,
We are not entirely convinced that this is an Inchworm, a name along with Spanworm given to the caterpillars of moths in the family Geometridae because of the way that they crawl.  According to Bugguide:  “larvae generally have only two pairs of prolegs (at the hind end) rather than the usual five pairs in most lepidoptera; the lack of prolegs in the middle of the body necessitates the peculiar method of locomtion, drawing the hind end up to the thoracic legs to form a loop, and then extending the body forward.
”  The caterpillar in your photo has three pairs of prolegs, which is fewer than the five possessed by most caterpillars, hence its method of locomotion.  BugGuide only indicates that “larvae generally have only two pairs of prolegs” which might mean that some individuals have three pairs.  Your caterpillar also reminds us of that of the North American Funerary Dagger Moth which is depicted on BugGuide.  We will attempt to get you a species identification, and until we determine otherwise, we will archive your letter with the Inchworms.  Perhaps we can enlist assistance from our readership towards a conclusive identification of this interesting caterpillar.

Unknown Caterpillar

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the hungry catapllers
Location:  satellite beach, fl
August 8, 2010 8:42 am
i found these hungry catapillers. eating away at what left of bushes in my front yard. All I know they black and green with legs in front and back.
neal

Snowbush Spanworms

Hi Neal,
Though we were not familiar with this caterpillar, we quickly identified them as Snowbush Spanworms,
Melanchroia chephise, the caterpillar of the White-Tipped Black, because the caterpillars appeared to have but two sets of prolegs at the hind end, indicating the family Geometridae.  BugGuide provides this information:  “larvae feed on plants in the spurge family (Euphorbiaceae) such as Breynia and Phyllanthus species.”  We are having a difficult time believing these caterpillars have defoliated your shrubs as depicted in your photographs.  We suspect a rampant chain saw was the real culprit.

Snowbush Spanworm

What's That Bug? does not endorse extermination