Arachnologische Mitteilungen 54

42 A. Hirna pitfall traps, entomological sweep-netting, hand-collecting, and with the aid of pooter. The specimen of Mermessus trilo- batus was found at only one locality. The photograph of Mermessus trilobatus was taken using an Olympus DP72 camera connected to an Olympus SZX10 stereoscope (Center for collective use of the scientific equip- ment, National Museum of Natural History, NAS of Ukraine, Lviv). Discussion The range of Mermessus trilobatus is continually spreading out from Germany, where the species was introduced in the late twentieth century. However, this species has now been found not only in Western Europe, but also in most of Cen- tral Europe (Poland, the Czech Republic, Slovakia, Hunga- ry, Slovenia, Croatia) (Fig. 3; Dolanský et al. 2009, Kůrka et al. 2010, Rozwałka 2010, Košulič & Hula 2011, Holec et al. 2012, Čandek et al. 2013, Košulič et al. 2013, Rozwałka et al. 2013, 2017, Hula et al. 2014, Niedobová & Hula 2014, Republic of Croatia 2014, Dudić, 2015, Kovács & Szinetár 2015, Kovács et al. 2015, Szinetár et al. 2015; Šestáková et al. 2017; CAS 2017). There is a higher concentration in Wes- tern Europe (France, INPN 2017) and in Central Europe: i.e. Switzerland (CSCF 2017), Germany (Arachnologische Gesellschaft 2016), the Czech Republic and western Poland (Rozwałka et al. 2017). In the Carpathian Mountains Mermessus trilobatus is known within Poland (Gajdoš et al. 2014) and Slovakia (Šestáková et al. 2017: heated greenhouses in the Botanical Garden in Košice). In Poland (Tatra National Park) one fe- male has been found in the glacial cirque of the Gąsienicowa Valley around the lake Litworowe Staw (ca 1700 m a.s.l.; Rozwałka et al. 2017). In other words, under conditions simi- lar to the presently documented locality of this species in the Svydivets’ mountain massif in Ukraine. Mermessus trilobatus belongs to the smaller linyphiids, with an average body length of 1.6-2.1 mm. It is a eurytopic species, capable of successfully spreading in the air by bal- looning (Dolanský et al. 2009, Rozwałka 2010, Blandenier et al. 2013). In North America the species inhabits both diverse natural habitats and heterogeneous habitats changed by hu- man activities (Millidge 1987). The ability to live in a wide variety of ecosystems and to tolerate a wide range of envi- ronmental conditions, together with a strategy of aerial dis- persal, allows Mermessus trilobatus not only to survive in the temperate climatic belt of Europe, but also to spread quickly and easily. Currently the species is found in nearly all types of more or less open habitats. Our knowledge of the overall impact of an alien species on European spiders is low, in particular on the small number of alien species that can exist in natural habitats (Nentwig 2015). The influence of an invasion of Mermessus trilobatus on the structure of spider communities and the functioning of associated ecosystems remains an open question. It is not known whether it replaces native species, becoming part of the regional fauna. Therefore, at this time we can only accu- mulate data based on the initial country records of Mermessus trilobatus , and conduct long-term monitoring of spider com- munities at these localities. Acknowledgements The author is especially grateful to V. Lyesnik (Lviv,Ukraine) for help during the collecting of the arachnological material and to B. Jareckyj (Scotland, UK) for linguistic help. An anonymous reviewer, Dr. A. Hänggi (Basle, Switzerland) andT. Blick (Hummeltal,Germany) are thanked for their comments on an earlier version of this manuscript. References Aminal 2000 Evaluatie van het actuele heidebeheer Limburg. – Aminal-Dossier 5: 1-11 Arachnologische Gesellschaft 2016 Atlas der Spinnentiere Europas. – Internet: https://atlas.arages.de (12.12.2016) Balogh J 1940 Zur Kenntnis der Spinnenfauna der Nordostkarpaten. – Fragmenta Faunistica Hungarica 3: 71-74 Fig. 2: Mermessus trilobatus , male palp, retrolateral view (from the Svydivets’ moun- tain massif, Ukraine; Scale 0.1 mm) Fig. 3: Map of known records of Mermessus trilobatus in eastern Central and Eastern Europe (see text for references). In the shaded area, the spe- cies is widely distributed and found at many localities.