Red Inchworms (Inch Worms)

red inch worm
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A reader wrote to us a while back about an interesting red worm that he found. He took a picture of the creature (see below), which shows a relatively small red worm in what appears to be an arid environment. The picture captures the red worm mid-movement, showing the middle of the worm’s body raised in an arc, which led the reader to suspect that he found an inchworm (commonly spelled as two separate words – “inch worm” – and also called a “measuring worm”). We have no reason to doubt this hypothesis, so below we provide some basic information about inch worms, although for reasons that we explain we aren’t sure exactly what the red inchworm our reader found is.

As always, let’s take a look at the picture the reader submitted first:

red inch worm

Because the photo is taken almost exactly above the creature, it is a little difficult to see the arc in the middle of its body. However, it you look closely, you’ll see that the middle of its body is in fact raised above the ground, causing the body segments before and after the curved middle section to scrunch together, and moreover the shadow cast by the worm implies that its body is forming an arch of sorts.

This is key, as it does suggest, in line with what the reader said, that he found some species of inchworm, which are actually not worms, but the larvae of geometer moths, making them caterpillars. (Caterpillars are simply the larval form of moths and butterflies.) Inchworms have no legs or prolegs in the middle section of their body, causing them to move in a distinct way. An inchworm will use its front legs to grab the ground and draw its posterior end forward, which makes the middle part of it bend upward. The prolegs on the hind end of the caterpillar then clasp the ground, allowing the front end of its body to reach forward to clasp the ground again. The inchworms movement makes it appear as if they are measuring the ground, or you might say the worms inch along, and hence their common names. Indeed, the taxonomic family that inchworms compose is called “Geometridae”, the Greek roots of which mean “earth measurer.”

The reader wanted to know exactly what kind of inch worm he found, but this is an extremely difficult question to answer. There are about 35,000 species in the family Geometridae, which makes identifying any given one very hard. There are certain inchworms that are particularly famous, such as spring and fall cankerworms (Paleacrita vernata and Alsophila pometaria, respectively), which can cause severe damage to trees, but neither one of these looks much like the inchworm our reader found. If the reader had sent more identifying information, such as where he found the inchworm, we might have better luck narrowing the options, but as it stands we can only say that we do believe he found an inchworm.

Of course, we can’t be entirely sure even of this (the worm-identifying beat doesn’t lend itself to certainty), but all the information we have points to this conclusion. If our reader still wants to find out more, we urge him to keep searching through different species of inchworms using whatever additional information he may have at his disposal. He very well could come across the precise species he found.


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4 thoughts on “Red Inchworms (Inch Worms)

  1. Brought in some flowers put in water when they died I took them out of glass noticed 2 little reddish brown inch worms had only seen green b4 didn’t throw away thought maybe not drowned left in cop drained all water after sun stated to go down I looked again sure looked dead. But touched with very lite finger one moved just alittle hes resting on towel night is coming on I don’t want him to get lost in house but will it be too cold for him to go bk outside? Or wait for morning I guess I won’t be getting an answer so I’ll wait for a m & hope 4 best?

  2. July 12, 2019 I had a tiny red inchworm on my thumb nail after I had been slicing red strawberries. I carefully took it outside to place on my deck plant holder frame and checked seconds later to see the inchworm turned the color of my stained deck of reddish brown. However the inchworm may have been drying up so I placed it inside my plant pot where it was moist. I looked for it shortly afterwards but could not see it. This is the first time I have ever seen a red inchworm.
    I live in Northeastern New York close to the Canadian Border.

  3. This morning while walking my dog beneath my apple trees a worm similar to an inch worm, but dark red fell out of a tree and landed on my fore arm. I ignored it until I felt it bite and looked down to see if it was a mosquito, but it was the worm and it was standing head down with its tail curled and then straightend out and stood straight an the sting intensified until I swated it.
    I have never seen one of these before and it left a small red spot on my arm, where it bit..
    I live in a rural area in Michigan.

  4. I found a red “worm” on the middle of the living room carpet this morning. (4/13) Picking it up, it was dead, limp, and very moist. It left a red stain on the carpet which did clean upon rubbing with cleaner.
    It is 2 centimeters long, with a hint of a “hook” at one end and a larger part in the middle. Its thickness is about 1/3 of a centimeter.
    What might it be and how did it get there. We do have a nice yard and trees.

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