Forcipule

Forcipules are the modified, pincer-like front legs of centipedes that are used to inject venom into prey.¹² They are the only known examples of front legs acting as venom injectors.¹³

Forcipules go by a variety of names in both scientific and colloquial usages. They are sometimes known as poison-claws or jaw legs,⁴ referencing their evolution from maxillipeds, a term which they are also sometimes known by in the context of centipedes (maxillipeds, maxillipedes). Other names include prehensors, telopodites, and forcipulae (singular forcipula).⁵⁶ In the specific case in which the forcipules are used to inject venom, they are called toxicognaths (from English toxic 'toxic' and Ancient Greek γνάθος (gnathos) 'jaw') ⁷

The term forcipule references their similarity with forceps.¹

Forcipules evolved from the maxillipeds - front-legs - of centipedes' last common ancestor, believed to be somewhat Scutigeromorph-like. They were initially leg-like, then progressed into a more pincer or claw-like shape, as seen today, and became restricted to horizontal movement.¹ The forcipules of modern Scutigeromorphs are the most significantly different in shape: they are more leg-like, and cannot hold prey in the way that they are used among other orders: they are used for envenomation only, making their use more comparable to a knife than a pincer.⁸