The scientific study of animal venoms covers a broad phylogenetic domain. We argue that the true extent of this domain has been obscured by researchers having overlooked the biological essence of venom. Venoms manipulate the physiological functioning of recipients to produce extended phenotypes that are beneficial to the venom producer and detrimental to its victim. The ability to produce extended phenotypes in living victims, such as prey paralysis, distinguishes venom from saliva. Understanding venom from this perspective substantially broadens the phylogenetic domain of venom to include taxa that use toxic secretions to feed on plants and manipulate sexual partners, and it paves the way for unifying the field of venomics with the fields that study invertebrate–plant interactions and sexual conflict.
