It only takes one of these caterpillars to royally ruin a perfectly good field day. Caterpillars like these are covered in irritating hairs to avoid predation. However, if a human has an unexpected encounter with one, it can result in an uncomfortable skin rash that can last from minutes to hours. Thankfully I found this one while walking on the path and was not subjected to its imminent wrath. 

[Photo and caption by Josephine Hubbard]

Sugiura, S., & Yamazaki, K. (2014). Caterpillar hair as a physical barrier against invertebrate predators. Behavioral Ecology, 25(4), 975-983.