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... et apparatus ingens belli; catapultae maximae formae centum uiginti,...

In ancient Greek and Roman siege artillery, the distinction between a catapulta and a ballista often comes down to the specific era being discussed, as the terminology famously inverted between the Classical Greek/Hellenistic period and Late Antiquity/Livy's time.However, during the Middle to Late Roman Republic (the period covering Livy's account of Scipio at New Carthage):1. Mechanical Distinction in Republican Rome (Livy's Era)Both machines were torsion engines—powered by tightly twisted skeins of animal sinew or human hair—but they were optimized for different trajectories and projectiles:Catapulta (Bolt-Thrower / Arrow-Shooter):Projectile: Heavy wooden arrows, bolts (doliola), or javelins.Trajectory: Direct, flat, pin-point line-of-fire.Primary Role: Anti-personnel weapon used to pick off defenders on city walls or clear ramparts before an assault.Ballista (Stone-Thrower):Projectile: Spherical stones (lapides) or incendiary balls, ranging from 5–10 lbs up to 100+ lbs.Trajectory: High, arched lobbing trajectory.Primary Role: Structural destruction (smashing crenellations, wooden hoardings, and siege towers) or indirect bombardment over city walls.2. Context in Livy 26.47This functional difference explains why Livy enumerates the captured arsenals of New Carthage separately:120 catapultae maximae formae + 281 minores: A vast collection of heavy and light bolt-launchers, designed for defense of the city perimeter.23 ballistae maiores + 52 minores: A smaller inventory of heavy stone-throwers, capable of damaging approaching siege engines or ships.3. The Historical Terminology SwapTo add to the confusion, the terms swapped roles over time:PeriodBolt / Arrow EngineStone / Ball EngineClassical GreekKatapeltesLithobolos / PetrobolosRoman Republic (Livy)CatapultaBallistaLate Roman Empire (Vegetius, Ammianus)BallistaOnager (or Catapulta)By the 4th century AD, writers like Vegetius began using ballista for bolt-shooters (including portable frame-mounted versions like the carroballista) and catapulta or onager ("wild ass") for single-arm stone-throwers. In Republican Latin, however, catapult =