HERCVLES VICTOR (August 12 and/or 13❶❼)

Reconstruction of altar to Hercules VICTOR　　　　　　　　　

Just before the Nemoralia, there was a ritual at the Ara Maxima in honour of Hercules Victor, also called "Hercules Invictus". A heifer was sacrificed to Him at this location❷, where He himself had erected the altar to celebrate his victory over Cacus, a fire-breathing giant and son of Vulcanus who had stolen some of his cattle ❸.

Women were not allowed to attend the ritual for Hercules at the Ara Maxima, as an old priestess had angered the Club-bearer once by refusing to give him some water from the shrine of Bona Dea (whose cult excluded men) when He wanted to quench His thirst.❹

Terracotta stattuette of Hercules in a similar position as the Farnese Hercules.
Römisch-Germanisches Museum, Köln (Germany)

A large, wooden scyphus probably played a roll during the rite at the Ara Maxima❺. A scyphus  is a two-handled wine goblet on a low base, as opposed to a cantharus which has a higher base and is the preferred drinking receptacle of Liber Pater (Bacchus/Dionysos).❻

A scyphus (Ancient Greek: skyphos ΣΚΥΦΟΣ), the type of wine cup used by Hercules.
Römisch-Germanisches Museum, Köln (Germany)

A cantharus (Ancient Greek: kantharos ΚΑΝΘΑΡΟΣ) the type of wine cup used by Liber Pater.
Römisch-Germanisches Museum, Köln (Germany)

It is unclear whether the sacrifice of the heifer at the Ara Maxima happened on August 12th or 13th, but the nearby temple to Hercules Victor, near the Porta Trigemina, had its celebrations on August 13.❶❼



Sources:
❶ Hornblower, Simon et al. (2012) The Oxford Classical Dictionary. Oxford: Oxford University Press: p667.
❷ Varro. De Lingua Latina. 6.54.
❸ Ovid. Fasti. Book I, 548.
❹ Propertius. Eligies, book IV, 9.
❺ Eden, P.T. A Commentary on Virgil: Aeneid VIII. Cambridge: University Printing House: p96.
❻ Macrobius. Saturnalia. Book V, 11.16.
❼ Bonnefoy, Yves (1992) Roman and European Mythologies. Chicago: University of Chicago Press: p128.