In the world of arthropods, stingers are highly modified structures that house and inject venom. Predators primarily use stingers to subdue their prey. However, when threatened, these predators may also use their stingers in a defensive manner. These anatomical weapons have been found and studied in only two lineages of arthropods: scorpions and aculeate wasps. This study reports the discovery of a sting apparatus in a third group, a wood-boring cerambycid beetle. Onychocerus albitarsis uses its antennae to deliver a sting that causes mild inflammation in humans. We used scanning electron microscopy to search for evidence of secretory structures in the terminal antennal segment, and compared the antennal morphology with the telson of the buthid scorpion, Leiurus quinquestriatus. We found that both arthropods have two pores opening into channels leading to the tips of their sting apparatus. In the cerambycid, a filamentous chemical residue was visible within a pore. This is a remarkable case of convergent evolution: thus far, no other beetle is known to use a stinger to inject chemicals.