Scientific societies, particularly taxon-focused natural history societies, play a crucial role in the long-term curation, mobilization, and governance of biodiversity data. They provide both the necessary expertise and social continuity to ensure data quality, foster trust, and build community cohesion. In this paper, we highlight the contributions of a natural history society for arachnids in Central Europe, the Arachnologische Gesellschaft, by describing two complementary biodiversity data infrastructures it coordinates: the Atlas of the European Arachnids, a curated occurrence-based mapping portal, and ARAMOB, a curated research data repository for ecological community datasets. We outline how these portals were developed in close collaboration with experts, museums, and research institutions, and how they are technically linked to or embedded in national and international data infrastructures such as World Spider Catalog, NFDI4Biodiversity and GBIF. Through this case study, we show how scientific societies can function as trusted intermediaries between data producers, aggregators, and users ensuring the visibility, interpretability, and interoperability of biodiversity data. We conclude with recommendations for strengthening similar community-rooted, taxon-specific infrastructures for other organism groups.