Woolly Bear Caterpillar Sightings


Phone calls and personal inquiries this past week have been a lot about that “big woolly caterpillar” that has been seen ‘everywhere’.

The caterpillar being reported to me most often is a Salt Marsh caterpillar that will soon become a Salt Marsh moth. The caterpillars are larvae of a moth in the family Arctiidae. This species has many color variations from black with orangish-red markings to pale yellow to reddish-brown. Caterpillars are generally lighter in color and darken with age. The body is covered with tufted hairs or setae.

Lots of folks that I’ve been visiting with call these larvae “woolly bear caterpillars”. Indeed, there are numerous species of moths that are so-called woolly bears. The caterpillars get the name ‘woolly bears’ because of the numerous hairs on their body.

These Salt Marsh caterpillars are generalists and feed on broad-leafed plants. Like most caterpillars, they usually feed as a group when they are young, but as they grow older and larger they tend to disperse. Salt march caterpillars stay in the larval stage for about a month to a month and a half. Environmental conditions like food availability, moisture, and temperature affect how long the larval stage lasts. As they become full-grown, they begin to wander away from the host plant to find a protected site where they can spin a cocoon.

Why the large number this time? The simple answer is that when the conditions are aligned for all the eggs to hatch, we’ll see a tremendous number of specific insects. Right now, that specific species is the Salt Marsh moth. Typically, they can lay up to 1,200 eggs. So when conditions are right for a large hatch, we expect to have plenty of caterpillars.

Interestingly, it is typically the fall that populations of salt marsh caterpillars are highest. These caterpillars may be seen wandering around to either find other food sources when old sources are consumed or could be caterpillars in search of a protected place to pupate.

The stinging capability or skin irritation from its hairs is often assumed to be a fact. Entomologists will debate this assumption. One state Extension entomologist, Dr. Wizzie Brown, says, “Some entomologists claim that woolly bears can sting you or irritate your skin while others say that they cannot. She continues, “I think that it probably comes down to skin sensitivity. While I haven’t had problems handling woolly bears, it doesn’t mean that everyone has no reaction; others may have sensitivity to the caterpillar hairs.” Basically, the take-home lesson is to always be careful when handling unknown insects since you don’t know how you will react.

What’s the next outbreak of insects going to be? I haven’t a clue. But it is interesting to watch the weather patterns and how they affect what succeeds in our area.

Cary Sims
Cary Sims is the County Extension Agent for agriculture and natural resources for Angelina County. His email address is cw-sims@tamu.edu Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin.

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