Early Halloween? by Lindsey Konkel
10/24/07 08:33 PM Filed in: Essay
“Halloween
has come a bit early to Stokes State Forest,” I
thought as I pulled onto Flatbrook Road to start my
year at the School of Conservation. Giant gray
cobwebs engulfed tree branches all along the road. I
certainly wanted nothing to do with spiders that
could make such frighteningly large webs.
I soon found out that the webs on the trees were not built by spiders at all but by moths, rather the caterpillar or larval stage of moths. The perpetrators in this case are pale, skinny caterpillars known as fall webworm. The adult moths deposit their egg masses which usually contain hundreds of eggs on the underside of leaves. When the webworms hatch in late summer and early fall, the larvae work together to spin a large silken web, enclosing the foliage that they will feed on. As they grow, the webworms expand the web to encase more leaves. When they have had their fill, the webworms pupate and fall to the ground, where they will over-winter in the fallen leaves.
Though their webs are intimidating, the webworm is rather harmless. Prevalent throughout North America, the webworm is known to feed on more than 100 species of forest and shade trees. In New Jersey, walnut, American elm, hickory, maple, and fruit trees are the preferred hosts. Although small trees may become completely encased by their webbing, and persistent infestation may lead to excessive defoliation and limb dieback among individual trees, the webworm is considered a forest pest of minor significance. Thus, the fall webworm garners little attention compared to more lethal forest parasites such as the gypsy moth and the hemlock woolly adelgid that are responsible for decimating large populations of trees in the Eastern United States.
I soon found out that the webs on the trees were not built by spiders at all but by moths, rather the caterpillar or larval stage of moths. The perpetrators in this case are pale, skinny caterpillars known as fall webworm. The adult moths deposit their egg masses which usually contain hundreds of eggs on the underside of leaves. When the webworms hatch in late summer and early fall, the larvae work together to spin a large silken web, enclosing the foliage that they will feed on. As they grow, the webworms expand the web to encase more leaves. When they have had their fill, the webworms pupate and fall to the ground, where they will over-winter in the fallen leaves.
Though their webs are intimidating, the webworm is rather harmless. Prevalent throughout North America, the webworm is known to feed on more than 100 species of forest and shade trees. In New Jersey, walnut, American elm, hickory, maple, and fruit trees are the preferred hosts. Although small trees may become completely encased by their webbing, and persistent infestation may lead to excessive defoliation and limb dieback among individual trees, the webworm is considered a forest pest of minor significance. Thus, the fall webworm garners little attention compared to more lethal forest parasites such as the gypsy moth and the hemlock woolly adelgid that are responsible for decimating large populations of trees in the Eastern United States.