ANT PREDATION OF ERIOCRANIA MINERS IN A POLLUTED AREA

We tested the hypothesis that air pollution may affect population dens ities of birch-feeding leafminers via changes in ant predation. Foragi ng activity of three ant species (Formica rufa, F. fusca and F. lemani ), predation rates and population densities of both solitary and grega rious Eriocrania (Lepidoptera: Eriocraniidae) miners were investigated at 13 sites around the Harjavalta copper-nickel smelter, SW Finland. Ant species differed in their distribution patterns relative to pollut ion. However, the total percentage of birch trees foraged by ants (all species combined) showed no correlation with the distance from the fa ctory complex. As a result, no clear trends in predation rates were ap parent in relation to the distance from the pollution source for eithe r solitary or gregarious Eriocrania species. Densities of the solitary Eriocrania species tended to increase with the distance from the poll ution source whereas densities of the gregarious E. haworthi peaked cl ose to the factory complex. No corresponding differences in predation rates between solitary and gregarious miners were found. Ant predation , thus, did not explain density patterns of Eriocrania miners in the p olluted area.