Focus on Diana and Callisto (Bril) and discuss the Subject.
In Greek mythology, Callisto was a nymph, or the daughter  of King Lycaon, king of Arcadia (which was claimed by Hesiod). For the Romans, she was one of the virginal companions of Diana, who caught the eye of Zeus (Jupiter). As a follower of Artemis, Callisto took a vow to remain a virgin, as did all the nymphs of Artemis.
According to Hesiod, she was seduced by Zeus, and later, when she was already bearing his child, she was "seen by her bathing and so discovered." After this discovery, "[Artemis] was enraged, and changed her into a beast. Thus she became a bear and gave birth to a son called Arkas." According to the mythographer Apollodorus, Zeus disguised himself as Artemis or Apollo, in order to lure Callisto into his embrace. Likewise, according to the Roman Ovid, Jupiter took the form of Diana so that he might evade his wife Juno's detection, forcing himself upon Callisto while she was separated from Diana and the other nymphs. Callisto's subsequent pregnancy was discovered several months later while she was bathing with Diana and her fellow nymphs. Diana became enraged when she saw that Callisto was pregnant and expelled her from the group. Callisto later gave birth to Arcas. Juno then took the opportunity to avenge her wounded pride and transformed the nymph into a bear. Sixteen years later Callisto, still a bear, encountered her son Arcas hunting in the forest. Just as Arcas was about to kill his own mother with his javelin, Jupiter averted the tragedy by placing mother and son amongst the stars as Ursa Major and Minor, respectively. Juno, enraged that her attempt at revenge had been frustrated, appealed to Tethys that the two might never meet her waters, thus providing a poetic explanation for their circumpolar positions in ancient times.This story was a favorite subject for some 15th-century, 16th-century and 17th-century patrons and artists. This was possibly related to the opportunity this subject gave to paint nude subjects. In Bril's work, the small, Italianate, clumsy staffage figures are but a minor ornamentation to the landscape, the subject for which he became celebrated in Rome.
Callisto Jupiter Ovid Ursa Major Minor Diana nymph Lycaon Greek mythology Arcadia Artemis Apollodorus Hesiod circumpolar Arcas Zeus Tethys Apollo