They produce venom before they are one full day old. In the U.S., about 8,000 people are bitten by venomous snakes each year. Most recorded bites are from the Western diamondback rattlesnake. Scorpions have remained virtually unchanged for 450 million years. To the ancient Chinese, they were symbolic of evil and death.
Tarantulas use blood pressure, as well as muscles, to move their legs.
Water loss can be devastating to the spider because it lowers the animal's blood pressure, making it hard to walk. The most famous poisonous fish is the puffer, which has caused many human fatalities. It's considered a delicacy in Japan, but if prepared the wrong way, this fish can be deadly. Most venomous snakes replace their fangs every few weeks. Fangs wear out quickly, so up to six replacements are continually growing in each jaw.