Byers, J.A. 1993b. Avoidance of competition by spruce bark beetles, Ips typographus and Pityogenes chalcographus. Experientia 49:272-275.
Experiment to test for attack of Ips typographus and Pityogenes chalcographus in logs previously infested with these species

Abstract-- Bark beetles, Ips typographus and Pityogenes chalcographus, attracted by synthetic or natural pheromone to Norway spruce logs, Picea abies, preferred to colonize uninfested logs rather than logs occupied by these beetles, probably as a means of avoiding intra- and interspecific competition. The aggregation pheromone components of P. chalcographus, chalcogran and methyl (E, Z)-2,4-decadienoate, inhibited the attraction response of I. typographus to its pheromone components (methyl butenol and cis-verbenol), while the converse was not true. However, verbenone released from colonized bark inhibited pheromonal response of P. chalcographus.
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Chemical Ecology