This painting depicts the story of Diana, the virgin goddess of hunting and childbirth, and her favourite nymph, Callisto. The myth, related in Book II of Ovid's Metamorphoses, is unique in that it openly explores sexual desire between women.
Wilson’s painting portrays the moment that Diana banishes her beloved Callisto from the hunt. Callisto was one of a group of devoted female followers who hunted with Diana. Like the goddess herself, they vowed to remain virgins and never to marry. Callisto was utterly faithful to Diana. However, her beauty attracted the attention of Jupiter, King of the gods. Conscious of the nymph’s vow of chastity, he transformed himself into Diana, taking on the female form, to get close to Callisto and seduce her.
Callisto fell pregnant with Jupiter’s child. In the painting she is shown in a state of despair as her pregnant stomach is exposed to Diana by her suspicious companions. Diana’s rage at Callisto’s infidelity is conveyed through her outstretched arm pointing accusingly. Wilson probably borrowed this pose from Titian's famous painting of the subject (National Galleries of Scotland and the National Gallery, London).
The myth has been a popular theme with artists since the Renaissance. The moment when Jupiter transformed himself into Diana to seduce Callisto, provided a suitable context for artists to paint an all-female sexual encounter; as have scenes portraying the communal bathing of her naked nymph followers. Such images of naked women cavorting together, though intended for the enjoyment of a male audience, may also have been stimulating to female viewers. In folk tradition, Diana has been associated with nocturnal all-female gatherings, female sexuality and self-sufficiency. However, versions such as Wilson’s, that depict the moment of Callisto’s shame and banishment offer a more patriarchal interpretation of the myth, using it to visually demonstrate to women the social consequences of not remaining chaste or of seeking stimulation from each other. Fear of the corrupting influence of female-only ‘Dianic cults’ or ‘societies of Diana’, where women gathered by moonlight and sometimes confessed to have been involved in ecstatic or erotic ritual, has been reported from pre-Christian times.
In this painting, Wilson's figures are dwarfed by a view of Lake Nemi, twelve miles east of Rome. Lake Nemi was commonly known as 'Speculum Dianae' (the Mirror of Diana). Ariccia, situated in the woods below the town, was also the goddess's most celebrated shrine. Wilson made on-the-spot drawings of the lake when he visited Italy around 1754, though none of these drawings replicate the viewpoint in the painting precisely. The design is an adaptation of one of his first Italian landscapes, for which a work by Gaspard Dughet had been the model. It has been pointed out that the association of myth and specific landscape in this painting is unique in Wilson's work and reflects the taste of Henry Hoare of Stourhead, who bought a smaller version of the painting in 1758. This canvas, which is the largest known version of the design, may well be the Lake Nemi which Wilson exhibited, with "its companion", at the Society of Artists in 1761. At least by 1832, and perhaps much earlier, it was paired with an identically sized version of Diana and Actaeon, a subject which Wilson had first painted in Rome around 1754. When sold in 1859, it was described in the catalogue as "the famous picture".