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ST. LOUIS – The venomous southern flannel moth has made headlines across the region recently, but the truth is the overall risk they pose is very low. 

A southwest Missouri man was recently sent to the emergency room after an encounter with one of these stinging caterpillars which are more prevalent in extreme southern and eastern parts of the state, but its relatives can be found here. 

“There are flannel moths that exist throughout the state and most, if not all of them, pose some level of risk to people. They are all venomous. But for the most part, they’re not too dangerous,” said Tad Yankoski, senior entomologist at The Butterfly House in Faust Park. 

While the adult moths are not venomous, the caterpillars have hairs that work like hypodermic needles. They have chemicals inside of them to where if they get pushed against your body they break off and inject the venom. Overall, the risk is quite low. 

“The caterpillar is just trying to mind its own business. It’s only to protect itself against predators. It’s very rare that people get stung by them and it’s even rarer when it’s such a severe case. You pretty much have to pick it up and squeeze it,” Yankoski said. 

The Missouri Department of Conservation said these caterpillars “do not actively attack people, but if you brush against these caterpillars, stinging hairs, hidden among non-stinging hairs or spines can penetrate your skin.” If a person is stung by a southern flannel moth caterpillar they could experience stinging, itching, burning, a rash, lesions, dermatitis, swelling, fever, or even nausea.

MDC said southern flannel moth caterpillars have seven pairs of prolegs which are “fleshy, peg-like legs along the abdominal segments,” and all other butterflies and moth caterpillars have five or fewer pairs of prolegs.

The department said there are other fuzzy caterpillars that have stinging hairs, but that does not mean every fuzzy caterpillar has the ability to sting. They advise people to leave them alone, dead or alive, no matter what.

“They look a lot like baby Chewbaccas. They look cute. They look like almost little puppies,” Yankoski said. “As a general rule, if you ever see a furry or spiky caterpillar it’s probably a good idea to leave them alone. Most of them out there are actually totally harmless but there are a few that could ruin your afternoon or worse.” 

Caterpillars spend most of their lives deep in the leaves of trees and bushes because they don’t want to be found but during the fall they’re out looking for a place to spend the winter. If you come across a fuzzy or spiky one, it’s best to leave them alone despite looking soft to touch. 

The MDC also says that if you feel something drop on you while walking through the woods, that you pause and look before brushing it away in a panic. Forcefully brushing off a stinging caterpillar is more likely to leave behind those stinging hairs.

Click here for more information on the stinging caterpillar.