Mastigoproctus giganteus—often called the giant vinegaroon, giant whip scorpion, or grampus—is one of the most charismatic members of the order Thelyphonida. Despite their fearsome appearance, these arachnids are entirely non‑venomous and rely instead on a remarkable chemical defense: a spray composed of roughly 85% acetic acid, giving off a sharp vinegar scent. Their long, whip‑like flagellum, from which the group gets its common name, is not a stinger but a sensory organ that helps them navigate their environment. With weak eyesight despite having eight eyes, they depend heavily on their elongated antenniform front legs and powerful pedipalps to explore, hunt, and interact with the world around them.
 
Native to the southern United States and Mexico, M. giganteus thrives in arid and semi‑arid habitats where it can burrow deeply into the soil. These fossorial predators emerge at night to hunt a wide range of invertebrates—crickets, cockroaches, millipedes, and even other arachnids—and have occasionally been recorded taking small amphibians. Their pedipalps act like crushing claws, holding prey steady while the chelicerae tear it apart. In turn, they face predation from raccoons, coatis, armadillos, roadrunners, and even tarantulas, making their defensive spray a valuable deterrent.
 
In captivity, the species is admired for its gentle temperament and fascinating behaviour. Though imposing in size—reaching up to 40–60 mm in body length, or around 15 cm including the tail—they are typically slow‑moving and reluctant to use their spray unless severely provoked. Females are long‑lived and reproduce only once, producing a clutch of around 40 young that they guard closely until the juveniles are ready to disperse. Their combination of prehistoric appearance, unusual sensory adaptations, and unique defensive chemistry makes Mastigoproctus giganteus a standout species both in the wild and in the hobby.