Jacquelyn Collins Clinton, A Late Antique Shrine of Liber Pater at Cosa pages 25-27
All of the above marble sculptures were reused in the late antique shrine. The statuettes probably served originally as private statuary of a decorative nature placed in house or garden, from the ruins of which the worshippers of Bacchus removed them to their shrine. […] These works do not fit into the Bacchic religious context as readily as the reused marble sculptures representing Dionysus directly, since they all were probably found purely by chance. One can only speculate on the reasons for reusing them at all. […] The small bust of Hercules is represented with grape leaves stick into the fillet around his head. He has thus a Bacchic aspect which must have had an immediate and relevant appeal. […] The Lysippean type after which the Cosa head is patterned is related to that of the Herakles Epitrapezios where Herakles is shown seated and holding out a cup of wine in an attitude of heroic repose after having attained immortality. This image of Herakles’ repose goes back to the sixth century B.C. in Greek vase painting where he is shown resting under a tree; by the end of the century, the repose came to be expressed in terms of a banquet, often celebrated with Dionysus. […] The Roman Hercules, of course, loved his wine and he is shown in works of art also engaged in a drinking contest with Dionysus. The theme of the drunken Hercules, furthermore, accounts for his inclusion in the Bacchic thiasos from Hellenistic times on. It becomes very popular in Roman times where Hercules bipax appears in representations of the Bacchic thiasos on sarcophagi. The imagery in these representations is, of course, funerary, illustrating the Bacchic concept of the afterlife as a continuing joyful revel or banquet. […] Moreover, the close connection between Hercules and Bacchus goes beyond these mythological ties, for the two were worshipped together in a common cult at least as early as the sixth century B.C. throughout Macedonia and Thrace, including the island of Thasos, and their names or images are linked in several monuments found in this region during Roman times. They are linked in various other monuments from other parts of the Roman world as well, and they were patron gods of Leptis Magna, the birthplace of Septimius Severus, who erected a temple for them in Rome and had their images included on his coinage. […] Thus, the connections between Hercules and Bacchus are so many and varied, with a long history continuing through late Roman times, that to discover an image of Hercules in a Bacchic shrine is not surprising.