There are more than 34,000 species of spiders, and all are technically venomous. Only 20-30, however, pose a danger to humans, and it's usually only the female who causes serious harm. Twice as toxic as a king cobra, the beaked sea snake stores enough venom to kill 53 people. Of the 3,000 species of snakes worldwide, only about 300 are venomous. The black widow spider got its name because the female supposedly consumes her mate after breeding, but this generally occurs only in captive situations when the unlucky male has little room for retreat.
Venomous animals are immune to their own venom.
If two rattlesnakes of the same species fight, neither will be harmed by the venom they inject. Not all scorpions live in the desert. The Emperor scorpion, for instance, blends into the dark forests of tropical Africa. Rattlers do not always rattle before they strike. The taipan of Australia is considered the most dangerous venomous snake in the world.