Caterpillar Confusion
© Georgeann Hall
Jun 23, 2000
There is much confusion over the difference between several types of caterpillar pests commonly found in our landscapes. The most often confused are: Tent caterpillars, gypsy moths, bagworms, sod webworms, and bagworms. Its important to be able to identify these pests and not confuse them with other less harmfull species. To help with identification, I have included descriptions and websites with photos.
TENT CATERPILLARS
Probably one fo the most famous of the lepidopterous vermin, tent caterpillars are also one fo the most easily identified. Most of us are familiar with their silken nests constructed in the crotches of various trees such as cherry, applem, hawthorn, and others. Yet by the time we become aware of the nests, the caterpillars have reached adult size and are much more difficult to eradicate. So, a little understanding of the tent caterpillar life cycle will better prepare us for next spring's attack. The tent caterpillar begins life in a brown, foamy egg case which can be found encircling a twig on a favored tree. If you've had tent caterpillar problems this spring, then be on the lookout for these egg cases in the fall and winter. If found, scrape the eggs off or remove the twig. If left unharmed, the larvae will hatch during March or April. They then gather in the forks of trees and begin constructing silken nests which serve as nighttime shelter and protection. Tent caterpillars are hairy and black with white stripes running down the back and blue spots running between longitundinal yellow lines. The larvae leave the nests during the day to feed and can defoliate entire trees. After 4 to 6 weeks the caterpillars are full grown and begin to migrate and it is this migration that annoys most of us. The caterpillars climb buildings and other structures looking for a place to pupate. After 3 weeks, the adult moth will emerge and fly off to seek a mate, lay eggs, and die. The key to controlling the tent caterpillar is early detection. Very young larvae are much easier to handle than are adult caterpillars. So keep a wary eye on your trees early next spring, and you should be able to stop these insects before they get started. GYPSY MOTH
Often confused with the tent caterpillar, the gypsy moth is a much more serious pest with a different life cycle. Eggs hatch out of buff-colored hairy cases April to early May. During May and June, the larvae are very mobile and descend trees to rest during the day, and ascend trees to feed at night. Gypsy moth caterpillars will feed on over 300 species of trees but by far their favored host is oak and in some parts of the country entire stands of oak trees have been defoliated. Larvae enter the pupal stage during late June to July and after 2 weeks the adult moths emerge. Males, which are brownish grey, emerge a few days ahead of the females (you know how it is, women always take longer to get ready than men!) Females are white with black markings, larger than males, and flightless. Males fly to the females by following the odor of pheromones which the females emit. After mating, eggs are laid on treelimbs, tree trunks, rocks, and other structures. These caterpillars can be spread great distances when eggs are laid on vehicles and transported. The caterpillars also crawl everywhere in huge numbers and they can be heard munching away if one listens on a still night. Some people have even developed allergies to the hairs of these caterpillars. The gypsy moth has been treated in various ways but the most popular and safest methods involve using Bt (Bacillus thuringinesis) and IGRs also known as insect growth regulators. If you have had a gypsy moth problem in the past, observe yhour trees this fall for the presence of those hairy, buff-colored egg cases which can be scraped off of tree trunks, limbs, and buildings.
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