Why are seed cones of Swiss stone pine (Pinus cembra) not attacked by the specialized pine cone weevil, Pissodes validirostris? A case of host selection vs. host suitability

The pine cone weevil, Pissodes validirostris Gyll. (Coleoptera: Curculionid ae), attacks seed cones of most Eurasian pine species, except these of Swis s stone pine (Pinus cembra L.). Behavioural responses of adult weevils to c one volatile emissions of Swiss stone pine and to those of a common host, m ountain pine (Pinus uncinata Ram.), were compared in an olfactometer. Weevi ls were significantly attracted by the volatile blend emitted by mountain p ine, but Swiss stone pine volatiles elicited an inverse response, with most weevils moving in the opposite direction to the odour source. However, the majority of second instar weevil larvae that were extracted from mountain pine cones and transferred into Swiss stone pine cones were capable of deve loping to the adult stage. This suggests that Swiss stone pine cones do not contain strong feeding deterrents that could prevent larval development. T he possible factors involved in the absence of colonization of Swiss stone pine cones by cone weevils are discussed.