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Key words. Hymenoptera, Formicidae, ants, citizen science, crowdsourcing, distribution, Finland, Formica, Lasius emarginatus
Abstract. The distance from southern Italy to Denmark is about the same as the length of Finland from south to north. A study of the biogeography of insects, such as ants, would take a lot of effort and funding to sample the whole area. Here, a citizen science approach is used to obtain distribution records for mound-building Formica ants in Finland. This resulted in samples from 2,434 ant nests, of which 2,363 were for nests of the target species group. The data obtained helps defi ne the northern limits of the species in Finland and resulted in three new records for F. suecica Adlerz, 1902, which is a red-listed species in Finland. In addition, as a by-catch, a new imported species dispersed in a peculiar way was recorded in Finland: Lasius emarginatus (Olivier, 1792). Volunteer citizens are potential research assistants in the science of entomology.
introduction
The mound-building Formica ants are important key species in their environment. They are effective predators and also have a role in nutrient recycling (e.g., reviews in Robinson et al., 2016 and Frouz et al., 2016). In addition, their nests are coinhabited by a multitude of other arthropods, such as beetles, spiders and oribatid mites (e.g., Päivinen et al., 2002; Härkönen & Sorvari, 2014; Elo et al., 2016; Robinson et al., 2016).
Mound-building Formica ants make nest mounds or cover their nests with organic material, mainly needles, small twigs and leaves of shrubs. The distributions of these ants in Finland were studied earlier by Baroni Urbani & Collingwood (1977) and Collingwood (1979) using geographical and administrative units. More recently, Punttila & Kilpeläinen (2009) report the distribution of these species based on data collected during the tenth Finnish National Forest Inventory (NFI10, National Resources Institute Finland). However, the species distributions in four Finish large-scale ecoregions; in addition, the NFI10 data exclude northern Finnish Lapland (approximately 1/5 of Finland), thus, leaving one of the most interesting geographic areas unstudied. The NFI10 sampling targeted forest and forested mire plots, thus leaving other environments unstudied, therefore missing the main habitats for some mound-building species, e.g., the meadow-dwelling Formica pressilabris Nylander, 1846.
In order to obtain distribution data from all over...