Artificially-perforated holes in stems of small hogweed (Heracleum sphondylium L.) mimic ecosystem engineering by the parsnip webworm (Depressaria radiella Goeze)

We conducted a field experiment to determine if artificial holes perforated into stem compartments of Heracleum sphondylium mimic the natural situation with Depressaria radiella. At five locations near the city of Leiden, the Netherlands, H. sphondylium plants were exposed to different treatments: a single hole perforated in the first, second or third stem compartment, or in all three compartments. After three weeks, arthropod numbers were counted inside and around hogweed stems.