Has anyone noticed the parallels between Lamia by Keats and Hardy's Tess of the D'Urbervilles? One description of Tess still resounds in my mind:

She was yawning, and he saw the red interior of her mouth as if it had been a snake's. She had stretched one arm so high above her coiled-up cable of hair that he could see its satin delicacy above the sunburn; her face was flushed with sleep, and her eyelids hung heavy over their pupils. The brimfulness of her nature breathed from her. It was a moment when a woman's soul is more incarnate than at any other time; when the most spiritual beauty bespeaks itself flesh; and sex takes the outside place in the presentation.

Now Lamia is a snake-woman who is as attractive as Tess, who makes men commit rash acts without being unambiguously evil. Lamia deceives Lycius because she wants love, but she is willing to surrender her identity for his pleasure. Tess in a way wants to live up to Angel Clare's standards. And when the woman of their dreams turns out to be something else, both men are shattered. The end is tragic for both women: not because they are evil, but because of nature and circumstances (Tess was raped, Lamia was turned into a snake).