Egg-laying habitat selection of the invasive slug Krynickillus melanocephalus Kaleniczenko, 1851 (Gastropoda: Eupulmonata: Agriolimacidae)

Abstract

Invasive slugs cause damage to biodiversity as well as to horticultural and agricultural crops. To develop methods to mitigate problems with recently emerging invasive species, basic ecological knowledge about them in their new environment is crucial. We investigated the egg-laying substrate preference of Krynickillus melanocephalus in a laboratory experiment in which the slugs could choose between four different substrates. Slugs were mainly observed in contact with birch leaf compost, and less so with gravel, potting soil and sphagnum moss. Almost 90% of the eggs were found buried in birch leaves, although eggs were found also in the other substrates. In addition, we tested the winter survival of the eggs by examining their susceptibility to low temperatures. Eggs subjected to freezing temperatures did not survive, and at 8 °C, 60–70% of the eggs hatched after three months (640 degree days). In areas where K. melanocephalus is present, transporting any soil, gravel or compost material could potentially contribute to spreading the species. Particularly, leaf composts may warrant attention in this areas.