Sugaring for moths: why are noctuids attracted more than geometrids?

.1 The attraction of nocturnal moths (Noctuidae and Geometridae) to fermenting sugar baits and to volatile organic compounds formed in these baits was studied by field trapping in South Finland. 2 In general, noctuids were attracted synergistically to these compounds (i.e. a mixture of compounds attracted more moths than the summed attraction of the components of the mixture predicted). Geometrids were not attracted synergistically. A similar pattern, with a few exceptions, was obtained by specific evaluation of forty‐one noctuid and fifteen geometrid species. 3 The degree of synergistic response was correlated with the general morphology of the moths. The robust species (proportionally large thorax and small wings; most of the Noctuidae) were attracted synergistically, while the slender species (proportionally small thorax and large wings; most of the Geometridae) were only weakly or not at all attracted synergistically. 4 The ecological background of the morphology‐related synergism is discussed. It is suggested that the energy demands of the robust species are substantially higher than those of the slender species, thus leading to different foraging strategies.