These data represent insect abundances from the University of Reading’s eight-ring Free-Air Diesel and Ozone Enrichment (FADOE) facility in 2018 and 2019. The two CSV files represent datasets from experimental hypothesis 1 (Pan_trap_data) and hypothesis 2 (Oviposition_data), respectively. Hypothesis 1 determined the effects of air pollution (tropospheric ozone and diesel exhaust, individually and in combination) on the abundance of flying insects from pan traps when Brassica nigra flowers were both present and absent within each of eight FADOE rings. Hypothesis 2 determined the effects of the same air pollutants on the oviposition success of Pieris brassicae butterflies on young Brassica napus plants. See README file for a full description of each data file.