Inchworms are the larvae form of the Geometridae moth family. These caterpillars get their name from their peculiar method of moving. They have both front and hind appendages and seem to be measuring their next move each time they take a step. Depending on the species and region, they are also referred to as cankerworms, loopers, and spanworms.
Inchworms are usually green or brown in color. When a predator comes near, the caterpillars will stand on their hind legs in an attempt to blend in with the surrounding foliage. Some species are even able to change color from green to brown in order to camouflage themselves with the twig they are currently crawling on. Others will cover themselves in plant material in an attempt to stay hidden.
The inchworm is an agricultural pest and is reviled in some parts of the world. They can lay waste to many different crop species, especially trees, fruit bushes, and garden plants.
There are over 23,000 different species of inchworm, with over 1,000 of them being native to North America. Inchworms are appropriately named, as most of them are approximately 1 inch long when full grown.
The Inchworm Diet
Inchworms eat a steady supply of leaves, flowers, and fruits, either leaving holes in their food or mowing it down entirely. They have a hefty appetite and can be found eating alone or in large groups. There are a few plant and tree species where they are found most often, including:
- berry bushes
- oak trees
- pine trees
- maple trees
- fir trees
- hickory trees
- apple trees
Inchworms are also attracted to garden vegetables and herbs, such as:
- Brussels sprouts
Other related species of inchworm eat lichen or pollen, while a few even eat other insects. While in their cocoon form, the inchworms do not eat any food.
When winter nears, inchworms transform into a cocoon (also called the larvae stage). In the spring, they emerge as moths and consume nectar and other liquids, much like a butterfly. Short-lived moths may not have any need to eat. Once they have successfully mated or laid eggs, most moths cease to have a purpose and will die off.
How Do I Keep Inchworms Off My Plants?
Inchworms are an agricultural pest that can wipe out gardens and crops if left unchecked. Traditional pesticides may be effective, but many are harmful to humans, pets, and plants. Bacillus thuringiensis is a chemical-free alternative. This bacteria can be sprayed on the leaves of infected plants. It kills the inchworms once ingested.
To prevent a return, gardeners can spray their trees with horticultural oil to kill any eggs. The moths can be trapped by wrapping the infected tree trunks in sticky tape. Female moths land on the tree and walk up the trunk to lay eggs, becoming trapped in the process. Other natural prevention methods include attracting birds to your yard or introducing a parasitic moth species.
What Animals Eat Inchworms?
The inchworm has many natural predators, including yellow jackets, paper wasps, and ground beetles. By attracting these creatures to your garden, you can set up a natural defense mechanism against inchworms.
Many bird species also consume inchworms. You can avoid using pesticides by setting up bird houses instead! However, If inchworms have truly taken over a garden, professional intervention may be required.
What is the Life Cycle of an Inchworm?
Inchworms are just one stage of a three-part metamorphosis that occurs ever year. Female moths lay their eggs in late summer or fall. Each species has preferences for egg-laying locations, such as under tree bark, on branches, under a leaf, and so on. Some lay single eggs, while others lay dozens or hundreds in one spot.
In the spring, the eggs hatch and the inchworms emerge. The hungry larvae gorge themselves on leaves for about 2 to 4 weeks. When they’ve had their fill, they descend from the trees using silk threads. The inchworms burrow underground and form cocoons to enter their pupae stage.
Depending on the time of year that the pupae stage began, moths may emerge in late summer or early spring. Moths are unable to survive the winter and never live more than one year. Their sole purpose is to mate and lay more eggs for the next generation of inchworms.
What Are the Most Common Inchworm Species?
The peppered moth (Biston betularia) is perhaps the most well-known of the Geometridate family. The inchworms of this species are known for their ability to disguise themselves as twigs in both shape and color.
The peppered moth is a famous modern-day example of natural selection. Since the start of the Industrial Revolution, the dominant color of the moths have changed from white to black as a result of smog and pollution.
The chickweed geometer (Haematopis grataria) The inchworms of this species feed on clover, Polygonum, Stellaria, and other low-growing plants (as opposed to the tree-dwelling habits of many other species). The wings of the moths are stunning—a creamy-yellow color is highlighted by bands of pink or red.
The crocus geometer (Xanthotype sospeta) is another popular species that is native to North America. They can be found in Canada and most of the United States. They feature bright yellow wings with brown spots that blend in with the fall foliage. The inchworms can be found on herbs and bushes. They have the characteristic “twig camouflage” ability.
The photo featured at the top of this post is © iStock.com/DmitriiDivanov
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