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. 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) measurements 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 7". 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-10-ol. T. minor was also Coleoptem: Scolytidae. ~This study was made within the project "Odour signals for control of pest insects." 5Present address: VDP Laboratories, P.O. Box 1547, 1200 BM, Hilversum, The Netherlands. 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.

Reproductive isolation among four sympatric small ermine moths (Yponomeuta) is analyzed in terms of niches in the sexual communication channel. Potential pheromone components were identified from pheromone gland secretions ofY. evonymellus,Y. cagnagellus,Y. padelius, andY. vigintipunctatus by gas chromatography with flame ionization and electroantennographic detection and tested for behavioral activity in the field. The species were found to share (Z)-11-tetradecenyl acetate (Z11-14: OAc) in combination with varying proportions of theE isomer as primary sex pheromone components.Y. cagnagellus differs from the rest of the species by having only a small amount (1.5%) ofE isomer relative toZ isomer in its pheromone. The closely relatedY. padelius has a three-component pheromone including large amounts (ca. 400%) of (Z)-11-hexadecenyl acetate (Z11-16:OAc) in addition toZ11-14: OAc (100%) andE11-14: OAc (34%).Z11-16: OAc appears to reduce trap catches ofY. evonymellus andY. vigintipunctatus when added to the pheromone. Although these species are the two most distantly related European small ermine moths, they seem to share the same sex pheromone, i.e.,Z11-14∶OAc (+20%E) and (Z)-11-tetradecenol. Our interpretation is that this might have been the sex pheromone of the ancestor of today'sYponomeuta species.

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