The female of the species is more deadly than the male
Origin
A well-known line from Rudyard Kipling's poem The Female of the Species, 1911:
When the Himalayan peasant meets the he-bear in his pride,
He shouts to scare the monster, who will often turn aside.
But the she-bear thus accosted rends the peasant tooth and nail.
For the female of the species is more deadly than the male.