A snake in the grass is a pretentious, dangerous person such as a hypocrite, mole, or spy. This idiom draws on the danger of being bitten by an unseen snake in tall grass, likely because it was stepped on or felt threatened.
"Take heed" is a warning to pay attention, similar to "beware" or "be careful." Compare "Therefore let him who thinks he stands take heed lest he fall." (1 Cor 10:12, NKJV).
Definitions for both idioms, from The Free Dictionary, are linked to below.
Answer
There are plenty of people around like this. You have to be careful who you trust, believe me, I know.
A False friend is just like a snake in the grass.
A "snake in the grass" is a person that should be regarded with suspicion because they are not trustworthy. An example of this idiom used in a sentence would be, "Natalie knew not to trust Nathan, he was a snake in the grass which would strike at the first available opportunity."
traitor, backbiter
The rattle snake lives in the grass.
It's only a grass snake
yes because the grass snake is bigger.
It means that you are the lowest of the low. You can't be any lower.
In the sentence the slimy, green snake slithered through the tall grass the nouns are snake and grass
I thought he was a friend, but he turned out to be a real snake in the grass.
The simple answer is you don't ! The Grass-snake, along with the European Adder and the Smooth Snake (which is actually a lizard) are ALL protected species.
depends on the type of snake it is and how long it lives
No the corn snake and the grass snake are completely different species ! Corn snakes are a native species of North America, while grass snakes are primarily found in Europe - including the British Isles.