Adult preferences of P. spadix were tested in a series of olfactory and tactile choice tests. Tests employed pine and beech wood blocks, which were undecayed or decayed by soft rot fungi, wetted with seawater or freshwater and drilled or undrilled. Survival of individual adults on undecayed pine and beech in a non-choice test was determined. Olfactory cues were found not to be an important factor in substrate selection. Adults were shown be negative phototactic, which is likely to be related to locating checks in wood from where colonisation can start. In the tactile tests adults clearly preferred wetted wood, although the water source was not important. Conditioned pine blocks were preferred over beech, with exception of seawater wetted wood on which no such a preference was found. The survival on pine was significantly higher than on beech, the water source had no influence on survival. It is thought that the water source relates to larval preferences or survival rather than that of adults. The fact that P. spadix is found along coastlines rather than rivers, is probably related to the effect of water type on larvae. P. spadix did not show a clear preference for marine when given the choice between two marine and one terrestrial soft rot fungus. Factors other than the fungal salinity tolerance are likely to influence preferences in P. spadix. The non-choice tests used undecayed wood blocks and showed significantly higher survival on pine as compared to adults without a substrate, indicating that fungal presence is not a prerequisite for colonisation by adults.

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