They’re called fall webworms even though their massive, silky webs appear in July and August across the landscape. This year, they seem to be making a big show.
While driving across Georgia last weekend it seemed to me that nearly every deciduous hardwood along the highway and in yards had a web or two and often more. A mix of favorable factors — high temperatures, abundant foliage and moisture — probably accounts for the large numbers this season.
Fall webworms actually are inch-long, yellowish-tan caterpillars with tough white hairs, orange bumps and a dark stripe along their backs and usually a red head (in Georgia). Each caterpillar becomes a fuzzy, whitish, brown-spotted moth (Hyphentria cunea).
An adult moth lays a cluster of a few hundred eggs on the underside of leaves. The eggs hatch in a week and the young caterpillars immediately start spinning their communal, loosely-woven web around foliage at or near the sunny tips of tree branches. Young caterpillars eat foliage inside the web, but older caterpillars will crawl out at night to feed and return to the web at dawn.
After feeding on foliage for about a month, the caterpillars leave their web for good, spin cocoons and pupate into adult moths in bark crevices or in soil. (They overwinter in the pupal stage.) The adults start the life cycle all over again.
In their webs, the caterpillars are relatively safe from predators. But when they leave the web, they are vulnerable to lizards, wasps and other enemies. Their hairiness makes them unpalatable to most birds — with the exceptions of yellow-billed and black-billed cuckoos.
Fall webworms often are confused with another species of communal web builders, Eastern tent caterpillars (Melacosoma americaneum), which appear in spring. Tent caterpillar webs usually are smaller, neater and located in the forks of tree branches.
IN THE SKY: From David Dundee, Tellus Science Museum astronomer: The Perseid meteor shower, visible through next Wednesday night, reaches a peak of about 50 meteors per hour this weekend in the northeast. Best viewing time: 2 a.m. until dawn. The moon will be full on Thursday — the “Fruit Moon.” Jupiter is in the south around dusk. Saturn rises in the east just after dark.
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