The Kerykion/Caduceus is the most important attribute of Hermes’ iconography. Adorned with wings and having multiple functions as a magic wand, herald’s staff, and shepherd’s staff, Hermes would be remiss if he left it somewhere. But there’s one question about Hermes’ staff that seems to be on everyone’s mind: what are the snakes for? As always, the answer to that question is not cut and dry.  
Mythologically speaking, there are two origin stories for the snakes on Hermes’ staff. The first one involves the seer Tiresias. One day while out for a walk, Tiresias saw a pair of snakes copulating and struck them with his staff, killing the female snake. This act offended Hera so much that she decided to punish Tiresias by turning him into a woman. Tiresias then spent the next seven years of her life living as a woman. Tiresias became a priestess of Hera, got married, had children, and even became a famous prostitute. This went on for sometime until Tiresias came upon another pair of snakes copulating. One version of the myth claims that Tiresias left the serpentine lovers alone this time while another versions claims that she struck the pair with her staff and killed the male snake this time. Either way, Tiresias was turned back into a man. Tiresias’ staff (along with the snakes that he killed with it) eventually found its way into the hands of Hermes and he has had possession over it ever since.  
A second possible origin story of the snakes on Hermes’ staff is comparatively shorter and less convoluted. One day, Hermes was going about his when he came upon a male snake and a female snake fighting. Wishing to stop the fight, Hermes cast his staff into the middle of the fray, successfully coming between the two animals. The snakes then entwined themselves around Hermes’ staff and began copulating. This particular myth is indicative of Hermes’ heraldic role as a harbinger of peace and glad tidings .  
On a more practical level, some scholars suggest that the snakes on Hermes’ staff are a fanciful reference to the white ribbons that hung off of the staves of heralds. Others suggest that the snakes are symbolic of prudence, life, health, and other related ideas.