In the mid-1800s a caterpillar the size of a human finger began spreading across the northeastern U.S. This appearance of the tomato hornworm was followed by terrifying reports of fatal poisonings and aggressive behavior toward people. In July 1869 newspapers across the region posted warnings about the insect, reporting that a girl in Red Creek, N.Y., had been “thrown into spasms, which ended in death” after a run-in with the creature. That fall the Syracuse Standard printed an account from one Dr. Fuller, who had collected a particularly enormous specimen. The physician warned that the caterpillar was “as poisonous as a rattlesnake” and said he knew of three deaths linked to its venom.