A turtle was happily swimming along a river when a scorpion
hailed it from the shore.
"Dear friend turtle!" called the scorpion. "Please let me climb
upon your back and swim me to the other side of the river!"
"No," replied the turtle, "for if I do, you shall sting me, and I
shall die."
"Nonsense!" replied the scorpion. "If I kill you in the middle of
the river, you shall sink, and I shall drown and die with you."
The turtle thought this over, and saw the truth of the scorpion's
statement. He let it upon his back and began swimming towards the
other side of the river. Halfway across, he felt a sharp pain in
the back of his neck.
"Why have you stung me?!" cried the turtle as his body began to
stiffen. "Now you shall die as well!"
"Because it is in my nature," replied the scorpion as the turtle
sank beneath the waters.
A variant of the "you knew I was a rattlesnake when you picked me
up" story.