Browntail moth caterpillar winter webs have been located and removed at the Isles of Shoals off of the New Hampshire coast, the first confirmed incident of the species in the Granite State in 75 years.

Browntail moth caterpillars have poisonous fine hairs that can produce skin rashes similar to poison ivy, even when the exposure is airborne. Inhaling the hair can also cause serious respiratory issues in some individuals. People should not handle the caterpillars without wearing proper gloves and, when possible, a mask.

Native to Europe, the browntail moth was accidentally introduced to North America in the late 1800s, eventually spreading to all New England states, New Brunswick and Nova Scotia. Massive federal work projects in the 1920s and 1930s, in cooperation with biocontrol research, reduced the infestation area to a small region along the Maine coast, but it has been expanding again in recent years. 

 Caterpillars can be identified by their dark brown coloration, fuzzy appearance and two conspicuous red-orange dots on their tail end.

 In New England, the moths’ caterpillar stage takes place from August to late June, however, between April and July is when the risk of exposure to their hairs is greatest. After that time, exposure to hairs that remain on surfaces can still take place but is less likely.

While oak and apple trees are primary hosts for browntail moth caterpillars, winter webs can also be found in coastal shrubs like beach plum and cherry, as was the case at the Isles of Shoals. The winter webs are small, tight clumps on two or three leaves at the tip of a branch and tend to be completely enclosed in silk. They form in the fall and can be removed any time between November and mid-April.

 For more information about how to identify browntail moth caterpillars and their webs, and to report any sightings, visit nhbugs.org.