Dipsas rubescens. Illustration by Thomas Hardwicke 1755-1835
Other names: Dipsade, Situla
The dipsas is a kind of asp, called in Latin situla.
A serpent with a bite said to produce intense thirst. The snake was the subject of a story told by several Greek authors, including Sophocles. According to the legend, Zeus was grateful to those who revealed to him the identity of the god who had stolen fire. He rewarded the informants by giving them the antidote to old age, which they packed onto the back of an ass that was then allowed to depart alone. The ass became very thirsty and stopped at a spring guarded by the snake. After first refusing him water, the snake then offered to trade it for the contents of the asss load. The snake, after receiving the contents, shed his skin, and the ass was relieved of his thirst. The word is from the Greek dipsás, a derivative of dípsa, "thirst."
"Tyrrhenian Aulus, bearer of a flag,
Trod on a Dipsas; quick with head reversed
The serpent struck; no mark betrayed the tooth:
The aspect of the wound nor threatened death,
Nor any evil; but the poison germ
In silence working as consuming fire
Absorbed the moisture of his inward frame,
Draining the natural juices that were spread
Around his vitals; in his arid jaws
Set flame upon his tongue: his wearied limbs
No sweat bedewed; dried up, the fount of tears
Fled from his eyelids. Tortured by the fire
Nor Cato's sternness, nor of his sacred charge
The honour could withhold him; but he dared
To dash his standard down, and through the plains
Raging, to seek for water that might slake
The fatal venom thirsting at his heart.
Plunge him in Tanais, in Rhone and Po,
Pour on his burning tongue the flood of Nile,
Yet were the fire unquenched. So fell the fang
Of Dipsas in the torrid Libyan lands;
In other climes less fatal. Next he seeks
Amid the sands, all barren to the depths,
For moisture: then returning to the shoals
Laps them with greed -- in vain -- the briny draught
Scarce quenched the thirst it made. Nor knowing yet
The poison in his frame, he steels himself
To rip his swollen veins and drink the gore.
Cato bids lift the standard, lest his troops
May find in thirst a pardon for the deed."
Lucan [1st century CE] (Pharsalia, book 9, verse 867-895)