Cuticular hair sensilla serve as mechano sensors (touch and flow-sensing) in many animals. They are some of the most sensitive sensilla known in the animal kingdom. The hair-like structures appear simple, but show striking sensitivity, specificity and mechanical robustness. It is unknown how architecture, composition (chitin-protein), and their hydration state contribute to the hairs function. Flowing up on our proposal SC 5187 we suggest to extend our study of the hair sensilla of the spider, Cupiennius salei to include the effect of water on the chitin-protein structure. To do so we plan to perform SAXS/XRD/XRF scans on fully hydrated samples (intact hairs and cross sections). With this we will be able to elucidate the effects of water on the structure of the hair sensilla. This work will pave the way for understanding the structure-properties-function relationships in arthropod sensors and will serve as archetype for bioinspired materials with embedded sensory functions.