Slovenia lies in Central Europe. At 20,273 km², it is among the smallest European countries. Four major European geographic regions meet here—the Alps, the Dinarides, the Pannonian plain and the Mediterranean. The majority of Slovenia is hilly or mountainous, with the exception of the eastern and northeastern regions. Forests cover approximately 55% of the country, makeing Slovenia the third most forested country in Europe. More than 40% of the surface is karstic. The country's extraordinary geographic diversity has resulted in a similar diversity of flora and fauna. Slovenia's well-defined phytogeographic regions include Alpine, Prealpine, Dinaric, Predinaric, Submediterranean and Subpannonian.
To date, 132 ant species have been found in Slovenia. Almost one third are distributed throughout the country and considered common (e.g. Myrmica rubra, M. sabuleti, Temnothorax crassispinus, Tapinoma erraticum, Camponotus ligniperda, Formica cunicularia, F. rufibarbis, F. sanguinea, Lasius flavus, L. emarginatus, L. niger). The Submediterranean region, where 103 species were found, shows the highest diversity of ant fauna. Thirty-one of all recorded species are known only from this region (e.g. Aphaenogaster epirotes, A. muelleriana, Crematogaster spp., Messor spp., Pheidole pallidula, Temnothorax exilis, T. flavicornis, Camponotus dalmaticus). Considering species general zoogeographic distribution, approximately two-thirds of Slovenian ants have Central- and Southern-European, European, Palearctic, or Eurosiberian zoogeographic affiliations. Ants of Slovenia's Submediterranean region include a considerable number of species whose range is largely limited to the Mediterranean portion of Europe. Monomorium pharaonis is the only introduced species and has become established in heated buildings.