The gypsy moth is one of the country's worst forest pests.

It attacks more than 500 species of deciduous and evergreen trees and spreads relentlessly once established.

The moths came to the U.S. in 1869 under controlled conditions but escaped and became established in 19 states.

Gypsy moths usually arrive in Washington as egg masses attached to outdoor articles such as picnic tables, birdhouses and children's toys brought from infested states in the East Coast and upper Midwest.

Some arrive on foreign ships docked at Washington ports.

After hatching, the moth larvae are dispersed by the wind or by attaching to something. The caterpillars quickly strip trees and plants of leaves, destroying some and making others susceptible to diseases.

They destroy wildlife habitat, degrade water quality and trigger costly quarantines of timber, agriculture and nursery products.

Besides the ports of Port Angeles and Port Townsend, traps are being placed at Priest and Hendrickson roads and at Autumn and Barnes roads.

For more information on Washington's gypsy moth control program, call the gypsy moth hotline at 800-443-6684 or visit the state Department of Agriculture's Web site at www.agr.wa.gov. Click on "Plants, Insects" on the page's left side, "Gypsy Moth" under the "Insect Pests" heading.