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Inchworms Vs. Caterpillars (7 Differences)

Most people are curious about inchworms vs. caterpillars because these two insects are frequently confused for one another. This is because they’re both insect larvae and can be found in similar habitats feeding on similar plants. These two creatures, however, are very different animals with very different ways of surviving in the world.

In this article, we’ll discuss some of the differences between inchworms and caterpillars, as well as how to identify both in the wild.

Inchworms vs. caterpillars

Here’s a list of 7 differences that exist between these two insects:

1. Inchworms don’t have legs in between

Cabbage looper
Cabbage looper | Photo by Justin Lauria on Unsplash

Inchworms don’t have legs in between their bodies, but they resemble caterpillars so closely that many people are confused. Inchworms have two to three pairs of true legs at the front of their bodies and another pair at the back called prolegs.

These legs function similarly to caterpillar legs in that they’re used for movement, grabbing, and hanging or attaching themselves to leaves or branches to camouflage. However, because they lack legs in between, they must stretch themselves in the desired direction and slide their rear prolegs towards the front legs in order to move. This movement is what gives them the name inchworms.

2. Caterpillars are much larger in size

Cinnabar moth caterpillar
Cinnabar moth caterpillar on plants | image by Lennart Tange via Flickr | CC BY 2.0

Another feature that distinguishes caterpillars from inchworms is their size. In comparison to inchworms, caterpillars grow much larger. Depending on the species, they may also have wider bodies.

Inchworms are small in size, with thin, long bodies and short legs. In fact, most geometer larva only grows to an inch in length, giving them the appearance of measuring an inch every time they loop to move, hence the name inchworm.

On the other hand, caterpillars can grow up to 5 inches in length, just like the larvae of hickory horned devils and atlas moths.

3. Inchworms grow as a moth of the family Geometridae

Inchworms are unique to the Geometridae family and don’t develop into adult species of butterflies or moths from different families as caterpillars do. They’re the larva of the moths from this family, very much like a caterpillar.

Although they’re both larvae, there are so many differences between them that experts decided to classify them separately.

The Geometridae family, also known as geometer moths or inchworms, is a large moth family with 23,000 species, 1400 of which are found in North America. These moths are distinguished by their uniform shape and stance. They have a butterfly-like appearance, and most have an average wingspan of 1.9 inches in length.

4. Caterpillars can be very colorful, but inchworms tend to be green or brown

Monarch caterpillar
Monarch caterpillar | Image by Wayne from Pixabay

The coloration of caterpillars often warns predators that they are poisonous and should be avoided. Most caterpillars have bright colors and patterns to help them blend into their surroundings. These colors range from dark brown, black, and blue to bright yellow, orange, and red.

This allows caterpillars to protect themselves from being eaten by birds or other animals and predators who avoid eating things that taste bad. On the other hand, inchworms are usually green or brown because they use their color to blend in with their surroundings.

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Green inchworms, for example, blend in with plants and leaves. Brown inchworms have the ability to blend in with dirt and branches. However, some species can also be light-colored, like the snowbush spanworm.

Since they have no other means of self-defense, inchworm’s coloration helps them hide from predators who might want to eat them. It also helps to protect the inchworm from predators that hunt by sight, such as birds, wasps, and beetles.

5. Long setae, spines, and tentacles are typically found on caterpillars

Hairy caterpillar
Hairy Caterpillar on a branch of tree | image by Bernard DUPONT via Flickr | CC BY-SA 2.0

Caterpillars frequently have long setae, spines, and tentacles. These things, however, may not be common among inchworms.

Some caterpillars have long, thin spines, while others have short, thick spines. Some use this to detect touch or movement in the air.

Caterpillars with long setae or tentacles on their bodies use it to protect themselves from predators. Before they mature into adult butterflies or moths, these features help in their survival in the wild.

Most inchworm species lack prominent filaments, setae, or spikes, except the horned spanworm, which has them attached to its back and uses them to blend in with its surroundings.

6. Inchworms go by many names

The term “caterpillar” usually refers to the larval stage of a butterfly or moth. But In contrast to caterpillars, inchworms have a variety of names based on their characteristics.

In fact, inchworms are also known as spanworms and measuring worms, whereas caterpillars are known only as caterpillars. Inchworms are also known as loopers, but not all loopers are members of the geometer family, and some are members of the noctuid family.

These names are derived from the fact that they loop to move forward, whereas caterpillars have a full set of legs and don’t need to loop in order to move. They can easily walk by moving their legs forward and in any direction they require.

Some caterpillars, however, have different names based on their appearance and other characteristics, such as the Banded Woolly Bear and puss caterpillar.

7. Both have different ways of mimicking for self-defense

Pitch pine looper crawling
Pitch pine looper crawling | image by Jerald E. Dewey, USDA Forest Service, United States via Wikimedia Commons | CC BY 3.0

The inchworm is a creature that mimics twigs to survive when threatened. In addition to their color, they can stay perfectly still and attach or hang themselves in branches or leaves to avoid detection.

The body of the inchworm is so thin that it resembles nothing more than a small branch or twig. An inchworm species, known as the camouflaged looper, even has the capacity to attach flower components to its back to mimic the flower it’s currently feeding on.

Caterpillars can mimic plant parts and other animals due to their different colors and appearance. Some have color combinations that make them look like bird droppings, while others have eyespots that resemble snakes.

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