Beautiful daughter of INACHUS and yet another object of ZEUS’s affections.
HERA had her suspicions when she saw this white heifer on a hill with a white cloud hovering over it whenever ZEUS went missing…
“ZEUS dear, I haven’t had a pressie from you for yonks,” she wheedled at the breakfast table.
“Anything you desire, dearest,” he smirked, “It’s yours.”
“Well now, there’s a lovely white heifer over on a yonder hill that would go so well with my prize herd…”
She saw ZEUS grow pale and his eyes cloud over. “I.. er, I er… Oh, yes of course darling.”
HERA employed ARGUS, her heavy, to act as a minder while ZEUS just had time to advise IO not to panic. “Hold on,” he whispered, “Somehow I’ll rescue you. I’ll get HERMES to do a little rustling.”
They nearly got away with it, but before ZEUS could get IO’s halter off, HERA sent a gadfly to sting the poor young cow to the point of madness. Bellowing with pain, she ran off with the fly in never-ending pursuit.
IO ran in every which direction to dodge her tormentor — over the hills and far away, up and down, in and over. She even passed PROMETHEUS chained to his rock on Mount Caucasus, who managed to shout as much encouragement as he could in the circumstances.
There came a time when she reached Egypt. As she and the gadfly paused for breath, ZEUS managed to return her to her original comely form, and she discovered she was pregnant.
She decided enough was enough. Egypt seemed a good place to settle. So she gave birth to EPAPHUS, yet another of ZEUS’s love children, and went on to become identified with ISIS and later LUNA.
We have no idea what happened to the gadfly.