Ongoing intensification and fragmentation of European agricultural landscapes dramatically reduce biodiversity and associated functions. Enhancing perennial non-crop areas holds great potential to support ecosystem services such as ant mediated pest control.

To study the potential of newly established grassland strips to enhance ant diversity and associated functions, we used hand collection data and predation experiments to investigate differences in (a) ant community composition (b) biocontrol related functional traits, and (c) natural pest control across habitats in cereal fields, old grasslands, and new grassland transects of three years age. 

Whilst all data regarding biocontrol related functional traits of ant species (b) are available within the publication and its supporting information files, we provide here our raw data of ant species activity and diversity surveys (a) and further the results of sticky card experiments as a proxy for biocontrol potential (c).

a) Ant activity and diversity were recorded using hand collections of worker ants with fine tweezers. Hand collection is considered the most efficient method for sampling ants (Gotelli et al. 2011), and is not biased in favour of behaviourally dominant species that monopolize food-resources (Andersen, 1997), which may occur when using bait traps. A total of three consecutive survey runs on each of the 90 sampling plots was performed, with 14 to 21 days between each run. On each sampling plot, two 1x1 m sized quadrants around the centre were searched for foraging worker ants for four minutes each per run. Worker ants active around nests were also sampled and the total aboveground nest activity (number of observed ants in steps of 10 individuals) estimated. Prior to the hand sampling, local vegetation cover (0-100 % of bare soil covered) was estimated visually in a radius of 2 m around the plot centre. All collected individuals were preserved in 70 % ethanol and identified to species level according to Seifert (2018), using a stereo-microscope at 10-fold magnification.

c) Biocontrol potential was measured using sticky-card experiments with adult Drosophila melanogaster (Meigen) flies as baits. Predation on fruit flies is well suited as a general proxy for pest control, because fruit flies are available in large numbers with a body size that allows all kind of different predators to prey on them (Lys, 1995). Further, fruit flies are easily re-detectable which allows data recording. Even though highly specialized and/or parasitic predator species might not be attracted when using fruit flies as baits, the results offer general interpretation, as pest control in farmlands is foremost provided by common generalist predators (Symondson, Sunderland, & Greenstone, 2002). We recorded each sampling plot with four consecutive survey runs (total of 720 observations/cardboards). On each sticky-card, thirty flies were glued to the upper side of a 6x8 cm cardboard, which had a plastic underlay (to protect the card from soil moisture), and fixed to the ground with a long nail. Flies were glued to the cardboard with well-diluted fish-glue enabling ground-dwelling predatory arthropods to remove the prey which guarantees successful predation (Lys, 1995). Each cardboard was covered by an enclosure with an appropriate mesh size (1x1 cm) to prevent access of rodents and birds and allow recording of arthropod predation on fruit flies (Hulme, 1996). Two cardboards were placed on each sampling plot per survey and exposed to predatory arthropods for 2-3 hours. Afterwards, predation rates (number of removed flies) and the estimated vegetation cover of the sampling plots (0-100 % of surface covered) were recorded directly in the field. We observed sticky cards for 10 minutes after exposure to the field, as well as during collection of the cards, to record (whenever possible) the identity of arthropod predators accessing the baits.