Venom types. Among the major classes of toxin in venoms are: Venom is widely distributed taxonomically, being found in both invertebrates and vertebrates; in aquatic and terrestrial animals; and among both predators and prey. The major groups of venomous animals are described below. Venomous arthropods include spiders, which use fangs — part of their chelicerae — to inject venom; and centipedes, which use forcipules — modified legs — to deliver venom; along with scorpions and stinging insects, which inject venom with a sting. In insects such as bees and wasps, the stinger is a modified egg-laying device — the ovipositor. In
Evolution of snake venom in several lineages, proteins that pre-digest prey, and a method to track down prey after a bite. These various adaptations of venom have also led to considerable debate about the definition of venom and venomous snakes. The idea that venom had a single evolutionary origin has been called into question by a 2015 study, which found that venom proteins had homologs in many other tissues in the Burmese python. The study therefore suggested that venom had evolved independently in a number of snake lineages. The origin of venom is thought to have provided the catalyst for the rapid diversification of