2025 Volume 28 Issue 2 Pages 125-131
The browsing ant Lepisiota frauenfeldi native to southern Europe has been introduced through human activities to broad areas globally since 2017. In areas it has invaded, the ant is known to rapidly increase its population and particularly to prey on native ant species. We conducted ant monitoring surveys once a month using a time-unit sampling method on two routes, Route A and Route B, at Nanko Port, Osaka, Japan between 2021 and 2023. On Route A, the browsing ant was observed with the highest frequency, accounting for 77 to 100 percent of the population throughout the survey period, and eight other ant species were observed. The number of Le. frauenfeldi individuals decreased from September 2021 to January 2022, peaked in June 2022, and hit a low in January 2023. On Route B, this ant was not observed at any time during the survey period, but ten other ant species were observed. The diversity and evenness of ants at the site that had been invaded were much lower than at the site not invaded, suggesting that the presence of Le. frauenfeldi had a negative effect on diversity and even distribution of local ants. In addition, we investigated the distribution of Le. frauenfeldi using the time-unit sampling method over the wider area of Nanko Port (375 ha), dividing it into 15 grids. Our results showed the browsing ant to be found only in grids in the southeastern part of Nanko Port. These results suggest that the species currently has a limited range in this area, highlighting the importance of early control measures before its distribution expands.
