I'm sure it's hard to be adventive, temporarily naturalized, that is.
-- Gish Jen, World and Town
Carrion beetles usually avoid competition with blowflies by visiting the carcasses at a later, dried stage of decomposition. Next come the omnivores, such as wasps and ants, and finally there are the adventive insects, like spiders.
-- David Shobin, The Provider
Adventive, like adventure, is derived from the Latin word adventus meaning “an advance.” The suffix -ive denotes a noun that comes from an adjective, like detective or active.