The Luxan tongue sting is a natural defense of the Luxan species. Luxans possess a very long tongue that they can quickly launch out of their mouths for several feet.
It is coated with a contact poison so that when the tongue hits someone it releases just enough poison to render the target unconscious. This poison is adaptive and has worked on everyone subjected to it no matter what species they were. ("A Constellation of Doubt")
Their tongue is also prehensile and with practice can be used to grab things and even swing from overhangs. ("Lava's a Many Splendored Thing")