Sampling design
At 22 dry grassland sites (Fig. 1), three pan traps (yellow, blue,
white; 19,6 x 15,4 cm with a 300ml 8%-Formaldehyde-water-dish
wash-solution) were attached to sticks approximately 40cm above the
ground in a triangle 1m wide triangle. The traps were installed for
three sampling campaigns in 2017: May (15/5-18/5/2017), June
(12/6-15/6/2017) and August (15/8-18/8/2017), located at representative
sites of the patches. Each trap stayed for 48 hours in the field within
each sampling campaign. The weather conditions were sunny and dry
throughout sampling campaigns.
Specimens were needled and determined to species level using Amiet et
al. (1999-2017) and Scheuchl (2000-2006) and van Veen (2010) and Bot and
van de Meutter (2019) for the hoverflies.