How do you tell if a caterpillar is poisonous?

Poisonous Caterpillars

WikiAnswers contributors share their caterpillar knowledge:

• Yes, there are lots. The ones with fur and of different colors are poisonous.
• The most poisonous are the saddleback caterpillar, the puss caterpillar, the Io moth caterpillar and the hag caterpillar; their spines are connected to poison glands on their body.
• A dingy yellow one isn't poisonous, but a bright yellow one can be, as can the green/red ones.
• Many are stinging and very troublesome if you come in contact with them. Most are very colorful, as to let you know to STAY AWAY! here is a great link from University of Kentucky which shows photos of some doozies!\