Wood ants play a keystone role in forest ecosystems by influencing the structure and composition of soil and forest floor vegetation as well as the abundance of other ground-dwelling arthropods and invertebrate foliar herbivores. Tree species composition and diversity of forest stands may have a profound effect on ants through changes in the structure of vegetation, abundance and diversity of prey, and the structure, moisture and temperature of the soil. However, little information is available on forest diversity effects on wood ants species richness, abundance and foraging activity. This project will explore effects of tree species diversity on wood ants in a long-term Satakunta forest diversity experiment (www.sataforestdiversity.org) established in SW Finland in 1999. The experiment consists of monocultures and different 2-, 3- and 5-species mixtures of conifers and broadleaves. The project will involve mapping the distribution of ant mounds, assessment of ant species richness, abundance and foraging activities, recording ants foraging on trees, and conducting ant-exclusion experiments. These measurements will be related to tree species diversity and composition of the plots as well as the abundance of foliar insect herbivores. This project offers the prospective student a unique experience of field work in a long-term large-scale forest experiment as well as training in use of various sampling techniques, experimental design, and data analysis.