Acrothoracican barnacle borings are reported for the first time from the Louisiana Limestone (Upper Devonian-Famennian) of Missouri. Evidence of barnacle attachment to and excavation of a live host shell is provided by secretory "blisters" on one brachiopod specimen and by the preserved life orientation of a barnacle-bored brachiopod. Post-mortem attachment of barnacles is indicated by the location of borings on the shell interior, hinge, broken shell surface, and cardinal area of the "blistered" brachiopod and by borings on the cardinal area of the pedicle valve of the brachiopod Syringothyris.