What Is It Wednesday: White-marked Tussock Moth Caterpillar

Name: White-marked Tussock Moth Caterpillar (Orgyia leucostigma)

The White-marked Tussock Moth caterpillar is abundant in eastern North America and its range extends as far west as Alberta. It measures about 35 mm in length and is covered by a variety of toxin-laden hair tufts. Black, quill-like hair strands stick out from both sides of its reddish-orange head, while the rest of its body is covered in spiky, black and white tufts.



Photo Credit: Barbara Riddell

It also has four round tufts on its back behind its head, which bear resemblance to little pom poms. These toxin-laden pom poms are also barbed, adding an extra bite should something come into contact with them. The toxin on the hair tufts is able to penetrate the skin, which can lead to allergic reactions in sensitive individuals, including redness, irritation, welts, and/or respiratory issues. It goes without saying that people should avoid skin contact with these caterpillars, but that’s not all! The cocoon spun by these spiky fiends is made of its own silk and hair. The toxin-laden hair woven into the cocoon can remain active for more than a year.

These caterpillars emerge in late June and remain present through to August. When overly large populations occur in a season, otherwise known as outbreak populations, much damage can be done. Outbreaks happen approximately every 15 years lasting for a duration of 2-5 years, which can cause severe defoliation of many plant species. Those most severely impacted include, but are not limited to, shade trees, orchards, Christmas tree plantations, and blueberry crops.

Fun Fact: White-marked Tussock Moth caterpillars are not picky eaters. They are known to feed on at least 140 species of deciduous and coniferous woody plants. Once this caterpillar finishes all the foliage on one plant, it will hang from its silk thread and wait for the wind to carry it to its next meal.

A big THANK YOU to supporter Barbara Riddell for sharing this photo with the TTLT community!