The aggregation pheromone of the ambrosia beetle, Trypodendron lineatum (Olivier), was isolated by MacConnell et al. (1977), identified as one of two isomeric, tricyclic acetals, and given the trivial name, lineatin. One of the isomers, 3,3,7-trimethyl-2,9-dioxatricyclo [126.96.36.199 4,7] nonane (4,6,6-lineatin), was synthesized in µg quantities by three different syntheses, assessed to be structurally identical to the isolated pheromone, and demonstrated to be highly attractive in field tests (Borden et al. 1979; Vité and Bakke 1979). The other structural isomer, 3,3,7- trimethyl-2,9-dioxatricyclo [188.8.131.52 4,7] nonane (4,5,6-lineatin), was not tested for biological activity. The enantiomeric composition of natural lineatin was not determined by MacConnell et al. (1977).