The western corn rootworm Diabrotica virgifera virgifera LeConte (Col.:Chrysomelidae) (D.v.v.) is one of the most important maize pests in North America. Ever since its invasion into Europe and its detection near Belgrade airport by BACA in 1993 it quickly spread all over southeastern Europe and is now advancing towards central Europe. Up until summer 2004 considered free of D.v.v., Germany is, with the exception of its northern and northeastern borders, surrounded by countries with proven D.v.v. infestations. In addition to simultaneous spot introductions by airplanes, three main routes for terrestrial introduction into Germany are likely: 1. from south to north via Lombardy (Italy) through Switzerland to the State of Baden-Wuerttemberg in the southwest; 2. from south east to northwest via Croatia, Slovenia, Austria into the State of Bavaria; and 3. from Belgium and the Netherlands in southeasterly direction to the state of Northrhine-Westfalia. From these, progress of D.v.v. along route 1 is so far the most advanced. It follows the well established network of road and rail connections through Switzerland and underscores the active role mankind and its technology plays as an active distribution vector for D.v.v. Mandatory crop rotation in the Swiss Canton of Ticino did slow down but could not prevent the northbound advance of D.v.v. in 2004. Considering the recent discovery of D.v.vu near the South German border, its introduction into German territory is only a matter of time and may be ecologically unavoidable. In Slovenla, another relatively small southern transit state, the D.v.v. population density is still much lower than in Switzerland but with significantly increasing trend during 2004 and with special emphasis in its southeastern provinces. Considering its relatively short distance to southeastern Bavaria and the well developed transalpine rail, road and tunnel system, Slovenia as a transit state may provide another access route for D.v.v. of lesser but still significant importance to Germany.