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 inch worms (also “inchworm”) are considered average while others are considered extraordinary. Inch worms 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, inch worms 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.
Much like spiders, some inch worms have the ability produce thin delicate lines. In some cases, these thin lines are made of silk. It just so happens that one of the most destructive types of inch worms, called cankerworms, produces soft silk threads as they drop from trees to evade predators. Also called measuring worms, cankerworms 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.
Another type of inch worm, also called Looper and 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.
Unfortunately, larvae eating habits cause massive destruction to food crop foliage. Simply put, larvae will eat as many holes as they can in the leaves of all kinds. Fortunately, there are several ways to control larvae/ inch worm infestations. 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 to help control infestations.
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