The Inchworm

The other day I had to stare, as an inchworm made its way along the railing of our deck.

Lacking all but two or three pairs of legs at the very front and about the same number at the very back, the inchworm’s method of locomotion is quite different from that of its fellow caterpillars, who seem to glide along on scores of  rapidly moving legs.

No, the inchworm does not glide; it inches.  First, the front stretches out.  Then the back is brought forward to meet the front, with the body in between looped upward.  The inchworm then stretches out again as the front is propelled forward.  Loop and flatten.  Repeat again and again.

Watching this entertaining process, I found myself wondering what evolutionary niche was filled or what advantage gained by the development of caterpillars with legs only at each end.  So I did a little research.

I didn’t find the answer to my question, but I did learn some interesting things about inchworms.  I learned that they are the larval stage of geometer moths.  The term ‘geometer’ refers to the way the caterpillar appears to ‘measure the earth’ as it moves.  And of the 35,000 species of geometer moth, about 14,000 are native to North America.

Unlike other types of caterpillars, inchworms are generally hairless.  Most are green, grey, or brown.  As soon as the inchworm hatches from its egg on the underside of a leaf in spring, it begins eating.  Inchworms typically eat leaves, although some species also eat lichen, flowers, or pollen.

After about a month of continuous feeding, the inchworm makes its way to the ground.  In early summer, the inchworm burrows into the soil and pupates.  It makes a cocoon of silk and soil near the earth’s surface.  The moth emerges in November and lays its eggs in the winter.

The inchworm has a great defense against predators–its resemblance to a twig.  This resemblance is heightened by little appendages that look like tree buds.  When disturbed, the inchworm often stands erect on its prolegs (back legs), further enhancing its twiglike look!–April Moore

3 Responses to “The Inchworm”

  1. Judy Says:

    Inchworm, inchworm, measuing the marigolds ….

    This is delightful, April. I love the ocntrast between the two photos. Two phases of the camouflage.

  2. Mary Ann Says:

    In the pose as a “twig” the inchworm just always makes me chuckle. The feeling of terror to avoid extinction in it is probably less than laughable TO IT — yet its disguise from predators is just TOOOO darn cute!

  3. April Says:

    I thank John Cochrane for sending me the link to this video of Danny Kaye singing about an inchworm! Thanks.
    http://www.youtube.com/watch?v=fXi3bjKowJU

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