The traps were plastic vessels with an upper diameter of 9.2 cm, a depth of 11 cm and a small opening at 4 cm below the border, to avoid rainwater overflowing, filled with 200ml of a conservative mixture of wine vinegar and 5% ascorbic acid. In all sites, three traps were set up in a line at a distance of 15 m from each other. In total, 51 traps were utilized.