A facehugger skitters around, seeking a viable host to impregnate.
It is a parasitoid form of the xenomorph exists solely to implant a chestburster embryo within a living host creature via their mouth. Once in range, the Facehugger will leap towards the host's face, often with alarming force and accuracy, and immediately wrap its tail around their neck and its digits around their skull. Once attached to a host, it inserts its proboscis down the victim's throat to impregnate them with a chestburster embryo over a few hours. After that, it lets go and dies.