No! Tent caterpillars are not poisonous or venomous. They do not produce venom and do not have the ability to inject it into predators or other animals. They do have setae, or small bristles, on their body that can cause irritation if they come into contact with skin. These setae can be dangerous to horses. When horses eat tent caterpillars, their setae can become embedded in the lining of the horse’s stomach, which can to a bacterial infection. The resulting infection can manifest as anything from mild indigestion to death.