Much like spiders, some inchworms have the ability produce thin delicate lines. In some cases, these thin lines are made of silk. Although certain types of inchworms can produce delicate lines made of silk, this worm is also one of the earth’s most destructive types of inchworms. Called “cankerworm,” this inchworm produces soft silk threads as they drop from trees to evade predators.
Cankerworms are also called “measuring worms.” They vary in color, but their bodies consist of long horizontal stripes. Cankerworms feed on shrub foliage and tree foliage. These creatures like to hang out in apples, elms, oaks, lindens, sweetgums, and a wide variety of other shade and fruit trees.
So what exactly is an inchworm? An inchworm is the larvae of moths of the family Geometridae (phylum Arthropoda, class Insecta, order Lepidoptera). This large, widely diffused group has more than 1,200 species indigenous to North America. Some inchworms (also “inchworm”) are considered average while others are considered extraordinary. Inchworms do, however, have many common characteristics. They have smooth, hairless bodies, and they typically grow up to one inch in length. Their colors run the gamut from brown and black to bright green.
Also referred to as loopers, measuring worms, and spanworms, inchworms have three pairs of legs at the front end and two to three pairs of prolegs or larval abdominal appendages at the rear. Inchworms travel by drawing their hind end forward while gripping the earth with its prolegs. They have the ability to stand erect and motionless when poked or prodded in any way.
Another type of inchworm, also called looper or cabbage looper, overwinters as green to brown pupae, tightly wrapped in cocoons (not webs) of white thread. In the spring, the adult moth emerges. The adult lays its eggs, typically on the surface of leaves. Once the larvae emerge, they feed for two to four weeks. Once they’ve had their fill, the larvae spin cocoons similar to the ones used during the overwinter process. The larvae prefer vegetable gardens and they eat a variety of crops including celery, cabbage, cauliflower, radishes, Brussels sprouts, beans, parsley, broccoli, potatoes, tomatoes, and peas.
Fortunately, there are several ways to protect your garden or crops from inchworms. Trichogramma wasps are natural predators as well as birds, yellow jackets, and paper wasps. They are also controlled by natural diseases and parasites. Wilt disease causes the worms body to rot. This usually happens late in the season. “Bacillus thuringiensis,” a wilt pathogen, is available to gardeners and farmer’s to help control infestations.