[entropy12]

Poisonous snakes have been perfecting their venom for over 100 million years. Do not fool with them. Even if you receive anti-venom in time, severe damage to the tissue around bite will occur.

Rattlers are not hard to avoid...they rattle!
Cobra’s will stand up a foot high to warn up with expanded neck line.
Coral snakes can be confused with the non-poisonous breed. If yellow meets the red, it is poisonous snake. Just like the yellow traffic light is warning red is next.

[ErnBatavia]

Rattlers are not hard to avoid...they rattle!

Not entirely true, unfortunately. We live in rattlesnake country, and wifey asks why I always walk around like a hunchback - it's the "Eyes down" thing goin' on.

[Joe 6-pack]

"If yellow meets the red, it is poisonous snake."

The mnemonic device used down here in coral snake country is:

"Red next to black is a friend of Jack. Red next to yellow can kill a fellow."

[steve86]

You can't depend on the rattle. People accidentally step on them and get bit not infrequently around here. Indeed, for the unfortunate Walmart shopper a month or two ago in Clarkston, WA (not far from here), who picked up the baby rattler in the garden section thinking it was a stick, did not get to hear a rattle.

A worse story yet is that a cobra climbed over the leg of my wife's dear sister in India while she was sleeping, but then slithered away uneventfully when the sister awakened with a start. It is not that unusual there to find a cobra in the house. There was never any threat display.

[SWAMPSNIPER]

If the rattle is wet you won’t hear a thing. They also break off, you may find a big rattler with nothing on it’s tail but a hard scale. All the rattles are is a collection of un shed tail scales. They don’t grow separately.