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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.
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Chiggers are the larvae of trombiculid mites and may inflict multiple intensely pruritic bites on their victims. They are parasitic only as larvae. They infest humans by crawling onto them and latching on. Proper clothing precautions and repellents are usually effective in reducing unpleasant chigger infestations.
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Centipedes are venomous arthropods that have one pair of legs per body segment. The 1st segment contains hollow curved “fangs” (really modified legs) bearing venom glands at the bases, which are capable of penetrating human skin. Centipedes generally use venom to kill prey but, when provoked, may envenomate humans and ...