Deroceras laeve Müll. (Mollusca: Limacidae), ein Eiräuber von Pegomyia betae Curt. (Muscidae)

Observations on the predacious activity of Deroceras laeve Müll. (Mollusca: Limacidae)on eggs of Pegomyia betae Curt.(Muscidae) and Epilachna varivestis Muls.(Coccinellidae). Deroceras laeve was observed feeding on eggs ofPegomyia betae in the laboratory and in the field. Since little is known about predacious behaviour of species of Limacidae, tests were conducted on the food preferences in two sets of experiments: (1) eggs ofP. betae on sugar beet leaves and (2) eggs ofEpilachna varivestis on bush bean leaves. Eggs ofP. betae were preferred over sugar beet leaf tissue (Fig. 1 and 2). The results showed that the slugs in addition to feeding on the eggs consume small amounts of the surrounding plant surface tissue. The feeding on eggs, however, was not considered to be accidential, because on leaves lacking eggs or on leaves with decreasing number of eggs,D. laeve fed predominantly on the tissue of the leaf margin. In the other set of experiments withE. varivestis the slugs were also found feeding on eggs, but showed a higher preference for plant tissue when compared with P. betae (Table 1).