As a herpetologist one of my biggest pet peeves is the incorrect usage of the words venomous and poisonous. Another huge pet peeve is calling an amphibian a reptile (but we’ll save that rant for another day ). Most people don’t understand that there is a difference between an organism being venomous or poisonous.
To be venomous an animal must be able to inject a toxin. The common delivery systems are fangs and stingers. The toxin is stored internally usually in a specialized gland(s). A great example of a venomous animal is a rattlesnake. All toxic snakes are venomous and not poisonous, well all of them except one. As with everything in nature there is an exception, the Asian tiger snake is both poisonous and venomous (see below).
Poison on the other hand is a toxic substance that is usually secreted from an organism’s external covering be it skin or leaves. Poisons are not injected instead they have to come in contact with skin or be ingested to cause harm. Poison dart frogs and poison ivy are examples of poisonous organisms.
So the next time someone yells that they’ve been bitten by a poisonous snake you can politely correct them while en route to the nearest hospital unless of course you are in the Asian tiger snake’s range. 😛