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.
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.