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Abstract

Bomb-radiocarbon analysis of modern carbon has been applied in many fields of ecology. The method allows determining the residence time of carbon in photosynthetic products and thus all organic matter in ecosystems. The atmospheric 14C signature will soon drop below the prebomb level due to fixation of atmospheric carbon in terrestrial and marine ecosystems and high rates of 14C-free fossil fuel combustion. Hence, the time is running out for bomb-radiocarbon application. Insect collections shelter an immense quantity of specimens stored in alcohol. We show how those specimens can be used for exploring the trophic structure of food webs by comparing their isotopic radiocarbon signature. Arthropods are one the most diverse and numerous groups of animals in many ecosystems. Their involvement in the trophic structure of an ecosystem is often poorly understood, but a good understanding of food web topology is indispensable to investigate and model how structural changes will affect ecosystem functionality (Dunne et al., 2002). The first challenge in analyzing trophic structures of arthropod communities lies in identifying the species and then, in the very labor intensive methods, to study their feeding habits. Recently isotopic methods have been recognized as useful tools to describe the often nontransparent linkages in the trophic levels of food webs. The most recent development was the application bomb radiocarbon by Hyodo et al. (2012) and Hyodo et al. (2015) impressively showing how this method could be applied to analyze the diet age of various invertebrates and even vertebrates. By analyzing the diet age, the study showed how intensively plant-based and detritus-based food webs are connected and how long it takes for carbon to flow through the web from primary producers to the consumers. Up to now applying bomb-radiocarbon in food web studies is the rare exception; however this method has become a standard tool in many other ecological studies looking on residence time of assimilated carbon in biological systems (e.g., Carbone et al., 2013; Muhr et al.,2013).