Lanne, B.S., Schlyter, F., Byers, J.A., Löfqvist, J., Leufvén, A., Bergström, G., Van Der Pers, J.N.C., Unelius, R., Baeckström, P. & Norin, T. 1987. Differences in attraction to semiochemicals present in sympatric pine shoot beetles, Tomicus minor and T. piniperda. Journal of Chemical Ecology 13:1045-1067.

Abstract-- The chemical ecology of host- and mate-finding in the pine shoot beetles, Tomicus minor and T. piniperda, was studied in southern Sweden. Beetles were collected in the field from defined attack phases on Scots pine (Pinus sylvestris). Using gas chromatography- mass spectroscopy, a number of oxygen-containing monoterpenes, e.g., 3-carene-10-ol, myrtenol, trans-verbenol, and verbenone, were identified from hindgut extracts of both sexes of both species. Compared to T. minor, T. piniperda contained additional compounds and in larger amounts. The amounts were highest in both species at the time when the beetles had bored into contact with the resin-producing xylem-phloem tissue. The synthesis of (1S,6R)-3-carene-10-ol by photooxidation of (+)-(1S,6R)-3-carene is described. In comparative electroantennogram (EAG) meausurements on males and females of both species, the most active of the tested compounds was trans-verbenol. Laboratory bioassays of walking beetles showed that T. piniperda was attracted to uninfested pine logs. T. minor was more strongly attracted to pine logs infested with females than to uninfested pine logs, indicating a female-produced aggregation pheromone. Field tests confirmed that T. piniperda was strongly attracted to pine logs. The attraction of T. minor to logs was significant only when logs were combined with racemic trans-verbenol and (1S,6R)-3-carene-ol. T. minor was also attracted to a combination of these monoterpene alcohols alone. We suggest that host and mate location in T. piniperda is achieved by means of a kairomone composed of host monoterpenes, while T. minor utilizes a primitive pheromone synergized by host odors. Evolution of host colonization strategies of the two beetles are discussed.
Chemical Ecology