As key soil ecosystem engineers, earthworms play a central role in soil processes and ecosystem services. Their behaviour and activity are strongly influenced by soil temperature and soil moisture, making them sensitive to changes in soil conditions. Although numerous studies have examined earthworm responses to soil conditions under controlled conditions, empirical data on their temperature preferences remain limited. Here, we present an experimental setup designed to identify the soil temperature preferences of earthworms. A two-dimensional terrarium constructed from plexiglass (100 cm x 10 cm x 1 cm) was equipped with five heat pads (SKU 41010841; 13 cm x 5.5 cm) evenly distributed along its length. Each heat pad was paired with a soil temperature sensor inside the terrarium, allowing independent regulations of soil temperature at each position and thereby generating a longitudinal temperature gradient. The entire setup was insulated and placed in a climate-controlled room with regulated temperature and humidity. For each experiment, two to four earthworms were introduced at different positions within the 2D terrarium, corresponding to distinct initial soil temperatures. Earthworm movement and distribution were monitored over a 72-h period to infer soil temperature preference. To approximate soil conditions typical of Sweden, the imposed temperature ranged from 5 to 15°C. Experiments are currently underway, and data analyses are ongoing. The resulting data will elucidate the preferred temperature range of Aporrectodea caliginosa and inform predictions of earthworm-mediated soil processes under changing climatic conditions.