THE DRAGON.
This creature entangles itself in the legs of the elephant which falls upon it, and so both die, and in its death it is avenged.
THE VIPER.
She, in pairing opens her mouth and at last clenches her teeth and kills her husband. Then the young ones, growing within her body rend her open and kill their mother.
THE SCORPION.
Saliva, spit out when fasting will kill a scorpion. This may be likened to abstinence from greediness, which removes and heals the ills which result from that gluttony, and opens the path of virtue.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.