Odorant-binding protein required for hygrotaxis behavior in humidity-detecting sensilla. Expressed in non-neuronal cells in hygrosensitive sensilla in the second chamber of the sacculus of the antenna third segment (at protein level). Viable with no morphological, mobility or chemosensory response defects (PubMed:30230472). Results in defective hygrotaxis behavior which might be related to increased desiccation resistance and overall longer lifespan (PubMed:30230472). Belongs to the PBP/GOBP family.