RT Book, Section A1 Zafren, Ken A1 Thurman, R. Jason A1 Jones, Ian D. A2 Knoop, Kevin J. A2 Stack, Lawrence B. A2 Storrow, Alan B. A2 Thurman, R. Jason SR Print(0) ID 1181051027 T1 Caterpillar, Mite, and Centipede Envenomation T2 The Atlas of Emergency Medicine, 5e YR 2021 FD 2021 PB McGraw-Hill PP New York, NY SN 9781260134940 LK accessmedicine.mhmedical.com/content.aspx?aid=1181051027 RD 2024/03/28 AB Caterpillar venom apparatus typically consists of barbed spines arranged in clumps or scattered on the dorsal surface of the insect. These are purely defensive in nature. Patients who are stung commonly have intentionally handled the insect or have had accidental skin contact while gardening. Envenomated patients typically present with acute pain followed by focal erythema and swelling. Caterpillars with a less sophisticated venom apparatus or low-potency venom may cause simple focal pruritus or urticaria, although some caterpillars are capable of producing a very painful sting requiring aggressive pharmacologic pain control. Systemic symptoms are rare. The puss caterpillar, or wooly slug (Megalopyge opercularis), is perhaps the most well-known and important venomous caterpillar in the United States. Wooly slug caterpillars have a widespread distribution, appear hairy and flat, and may reach a length of 4 cm.