Why did Goddess Aurora turn Tithonus into a grasshopper?

Aurora, in spite of her name, was not exactly the bright type.

She asked Zeus to grant Tithonus, her mortal lover, eternal life. Zeus accepted. But Aurora forgot to mention that she'd also like her lover to be granted eternal youth...

So Tithon went on living and on growing old. He became so old and so weak that he could hardly move anymore. He became a parched, immobile object - only his voice remained.

Aurora, taking pity on him, turned him into a grasshopper to end his suffering.

And every morning, grasshoppers now sing their love for the goddess of Dawn.