The following dataset contains fatty acid contents (in mg.g^-1 and in %), stable isotopes (‰), and compound specific isotopic analyses of carbon and hydrogen (‰) data for insects (terrestrial and semi-aquatic) and spiders collected around Lake Lunz (47°85’N, 15°05’E), Austria from June to September 2020. Measurements were done after storage at -80°C for 2 hours, and  freeze drying (24h), followed by taxonomic identification. Analytical details can be found in "Dietary availability determines metabolic conversion of long-chain polyunsaturated fatty acids in spiders: a dual compound-specific stable isotope approach" by Mathieu-Resuge, Margaux; Pilecky, Matthias; Twining, Cornelia; Martin-Creuzburg, Dominik; Parmar, Tarn-Preet; Vitecek, Simon; Kainz, Martin. Oikos (2021), DOI: 10.1111/oik.08513