Just in time for the “dog days of summer”: sources suggest that 3 August marked the Roman festival of Supplicia Canum, during which dogs were sacrificed and then paraded through the city to the temples of Juventas, or the God of Youth, and Summanus, the God of Nocturnal Thunder. It is believed that the Supplicia Canum sacrifice was in part a punishment against the creatures for their missed warning of the Romans during the 4th-century BCE Gallic Siege. Support for this explanation comes from that fact that, simultaneous with these sacrifices, geese, who had succeed in alerting the Romans of the approaching Gauls, were draped in elegant fabrics and paraded with pride.
Roman bronze dog furniture ornament, 1st century; Walters Art Museum.
“Cave Canem” mosaic, 1st century; so-called House of Orpheus, Pompeii.
Sources:
Howard H. Scullard, Festivals and Ceremonies of the Roman Republic (Ithaca, NY: Cornell University Press, 1981), 170.
Johannes Laurentius Lydus, Liber de mensibus (Lipsiae: B.G. Teubner, 1898), 4:114.