Poisonous spiders, scorpions, or caterpillars include:

• Black widow spider.
• Brown recluse spider.
• Scorpion.
• Puss caterpillar (woolly slug).

A toxic reaction can occur from a single bite or sting by a more poisonous insect or spider or from multiple bites or stings from a less poisonous insect or spider.

Most spider bites do not cause problems. However, a bite from a black widow spider or from a brown recluse can be serious and does require immediate medical care. Medicine to counteract the venom (antivenom) is available for black widow spiders bites.

Not all scorpions are poisonous. It is difficult to tell the difference between poisonous and nonpoisonous scorpions. All scorpion stings are treated as medical emergencies. Antivenom is available to counteract the sting of some scorpions.

Contact with most caterpillars does not cause problems. The puss caterpillar, or woolly slug, is the most poisonous caterpillar in the United States. Immediately remove broken-off caterpillar spines by placing cellophane tape or a commercial facial peel over the sting site and then pulling it off.