Jaculus

Also Known As: Latin iaculus, plural iaculi; the Greek equivalent is akontias, the javelin-snake
Region/Culture: Southern Europe
Mythos: Roman Mythology, Medieval Mythology
Primary Type/Nature: Monsters and Beasts
Mythical Attributes: It launches itself horizontally from a tree or a dead trunk with such force that it passes through a body like a thrown spear.
Role in Mythos: In Lucan’s account of Cato’s march through Libya the jaculus is one of the serpents bred from the blood of Medusa, and it is the one that kills without poison.
Relation to Humans: It kills people who walk beneath it, and it is the only snake in the Roman catalogue whose victims die of the wound rather than the venom. Medieval writers kept it in the bestiaries as an emblem of death arriving from above, without warning.

The stump stood in the sand with no branches left on it, dead wood bleached the colour of bone, and nobody in the marching column gave it a second look. Then part of it came loose. A length of it went out flat and fast across the heat, hit the standard-bearer Paulus above the ear, went through his head from temple to temple, and was gone into the scrub before the body had finished falling. No swelling. No blackened flesh, no thirst, no rotting limb. The wound was simply a hole, and the man was simply dead.

Lucan set that scene in the ninth book of his Civil War, the poem later known as the Pharsalia, written under Nero and left unfinished when the emperor ordered its author to open his veins. Cato’s soldiers are crossing the Libyan desert, and Libya in the poem is not merely hot but poisoned at the root. Perseus had flown home over it with the Gorgon’s severed head hanging from his fist, and the blood that dripped from it soaked into the sand, and the sand bred snakes. Every serpent in Africa is a drop of Medusa. Lucan lists them the way a quartermaster lists supplies: the swollen asp, the haemorrhois that opens every vein at once, the cerastes with its horns, the dipsas whose bite is a thirst no river can answer, the amphisbaena with a head at each end, the seps that dissolves bone along with flesh, the basilisk clearing the desert of its rivals by hiss alone. And in the middle of the list, five words, iaculique volantes, the flying javelins.

The killing itself gets four lines and no ornament. A fierce snake, the poem says, which Africa calls the iaculus, twisted out of the wood of a barren trunk, threw itself, drove through Paulus’ head and out through the temples, and fled. No venom acted there. Death came too fast for poison to matter. Then Lucan does the thing that makes the passage stick: he turns to the survivors and remarks how slow a stone from a sling looks now, how sluggish a Parthian arrow seems in the air. The soldiers have just watched a piece of the landscape outrun their own artillery.

Pliny, writing his Natural History a few years later, records the creature without a shred of poetry and without a hint of doubt. It is not only our feet that need fear serpents, he says. The javelin-snake hurls itself from the branches of trees, and these fly through the air as though shot from an engine. He means a torsion catapult. It is a working comparison from a man who had seen artillery, and it tells you exactly what he thought the animal was. Aelian, in Greek, calls it akontias and notes that the name is simply the name of the act: the snake flies with the speed of a javelin, so a javelin is what it is called.

That is the whole of it, and it is enough, because the name does all the work. Iaculum is the Latin for a throwing-spear, from iacere, to throw. The animal is not described. The animal is defined by its trajectory. The snake is the spear.

Solinus copied Pliny in the third century, adding that the iaculi climb trees and whirl down from them with great force, piercing whatever chance puts beneath. Isidore of Seville filed it in the Etymologies in the seventh century, where it belonged, since the entry is really an etymology with a body attached: iaculus is a flying snake, for they spring up into trees, and when some animal happens by they throw themselves onto it, iactare, and kill it, and that is why they are called iaculi. From Isidore the creature slid into the bestiaries and stayed there for five hundred years. The Aberdeen Bestiary gives it four lines around the year 1200, quoting Lucan’s tag; the Rochester Bestiary of about 1230 gives the same four lines, near enough word for word. Thomas of Cantimpré, wanting a scriptural hook, tied it to the arrow that flies by day and issued the snake with a pair of wings so that it could get up the tree in the first place.

Which is where the pictures come from. Nobody in antiquity said what a jaculus looked like: not its length, not its colour, not the pattern on its back. An illuminator with a page to fill cannot work with that, so he draws a small serpent, adds wings because the text keeps saying flying, and sometimes adds two forelegs to help it grip the branch. Do that often enough across enough manuscripts and a snake from a Latin poem ends up shelved among the dragons, which is roughly what has happened to it ever since. Leonardo da Vinci, drafting notes for a bestiary of his own, kept none of the ornament and only the mechanism: it stays above the plants, and launches itself like a dart, and passes through beasts, and kills them.

Its powers are the powers of a projectile, and they follow from a single decision the animal makes. It climbs. It waits along a branch where the game trail runs beneath, patient in the way that costs nothing, its weight settled on the sun-warmed bark, and it takes the measure of the ground below. Then it commits every ounce of itself at once. The lethality is not chemical, it is kinetic: a body converted into a point, arriving faster than the eye can track it, killing through bone. Armour is the wrong shape to stop it. The head of a Roman soldier does not stop it either.

The limits are the same limits any spear has. A thrown weapon is spent when it lands. The jaculus that has just gone through Paulus is lying somewhere in the scrub with nothing left to do, and it cannot repeat the trick without climbing something first, which means it needs height, a branch or a dead trunk, and a victim obliging enough to walk under it. On open sand it is a small snake with no particular gifts. Its venom, whatever it has, is beside the point, and Lucan says so outright. And its flight is not flight. It is a leap with a very good aim.

Real snakes do about half of it. The gliding snakes of Southeast Asia launch from branches, flatten their ribs into a ribbon and steer themselves through the air for the length of a tennis court, which is as close as evolution has come to the thing Pliny thought was routine in Libya. The name survives too, bolted onto an animal that could not have earned it: Eryx jaculus, the javelin sand boa, a stout little burrower of the Balkans and North Africa that spends its life underground and has never thrown itself at anybody.

Frequently Asked Questions

What is the Jaculus?

The Jaculus, or iaculus, is a serpent of Roman and later medieval legend that killed by launching itself from a tree or a dead trunk like a thrown javelin. Its Latin name comes from iaculum, a throwing-spear, and it is often called the javelin snake. Ancient writers treated it as a real animal of the Libyan desert.

How does the Jaculus kill?

By impact rather than by venom. In Lucan’s Pharsalia the Jaculus hurls itself from a barren trunk, passes clean through the head of the soldier Paulus from temple to temple, and flies off, and the poem states plainly that no poison was involved: the wound alone was fatal. This makes it unusual among the mythical serpents of the classical world, which almost all kill by poison.

Is the Jaculus a dragon?

Not in the classical sources, which describe it only as a snake. It became dragon-like in the Middle Ages, when bestiary illuminators had to draw a creature the texts never described and gave it wings, and sometimes two forelegs, so that it could climb and fly as the text said it did. That artwork is why the Jaculus is now usually grouped with dragons.

Where does the Jaculus live?

In the ancient accounts it is a creature of Libya and North Africa, lurking in trees along the routes that travellers use. Lucan places it among the serpents said to have been born from the blood that dripped from Medusa’s severed head as Perseus flew home over the Libyan sand.

Which ancient writers describe the Jaculus?

Pliny the Elder mentions it in the Natural History, Lucan gives it its famous scene in Book 9 of the Pharsalia, Aelian describes the same creature in Greek under the name akontias, and Solinus and Isidore of Seville pass it down to the medieval bestiaries. Leonardo da Vinci also noted it in his own bestiary jottings.