Olfactory cues and insects - scaling relations and immigration rates

Abstract: For herbivorous insects, location of host plants and habitat patches strongly depend on the type of sensory cue that is used during the search process and the probability of detecting a patch depends on the relative attraction between patches of different size. The visual impression of a patch increases predictably with the patch diameter and consequently, immigration rates of visually searching insects are often predicted by the scaling to patch size of visual cues. However, for olfactory cues, the relative attraction between small and large patches is unknown, but has been suggested to increase faster with patch size than visual information. In this thesis, I explore the scaling relation between olfactory cues and patch size. I measured odor attraction of patches of different size and estimated scaling rules for olfactory information. The estimated scaling rules were tested with simulations and a field experiment, where immigration rates of olfactory searching insects were quantified. The estimated scaling rules for olfactory information suggested that the relative attraction did not deviate fundamentally from the scaling of visual cues to patch size. Both the simulations and the field immigration experiment supported this suggestion. Therefore, I conclude that visual and olfactory cues scale roughly to patch size in a similar way, i.e. to the patch diameter. This thesis demonstrates the importance of considering species traits for the understanding of insect responses to habitat heterogeneity.