Although shell colour polymorphism of the land snail Cepaea nemoralis is a well-known phenomenon, proximate and ultimate factors driving its evolution remain uncertain. Polymorphic species show variation in behavioural responses to selective forces. Therefore, we estimated effects of various environmental factors (temperature, humidity, food availability, (micro)habitat structure and predatory pressure) on behavioural response (frequency of locomotion, climbing and hiding) of C. nemoralis morphs, in experimental and natural conditions. In the experimental part of study, the frequency of locomotion was negatively affected by temperature and the presence of food and positively influenced by the presence of light. Morphs significantly differed in behavioural responses to environmental variability. Pink mid-banded and yellow five-banded morphs climbed less often and hide in shelter more often than yellow and pink unbanded individuals when temperature was low and food was absent. Snails fed most often at moderate temperature compared to low and high temperatures. Field investigations partially confirmed differences among morphs in frequency of climbing, but not in terms of probability of hiding in sheltered sites. In natural colonies, temperature and (micro)habitat structure significantly affected frequency of climbing as well as hiding in shelter. Snails more often hid in sheltered sites where thrushes preyed on Cepaea. Tendency of unbanded morphs to climb trees may have evolved under avian predatory pressure as thrushes forage on a ground. Tendency of banded morphs to hide in sheltered sites may reflect prey preferences for cryptic background. The results implicate that differential behaviour of C. nemoralis morphs compensate for their morphological and physiological limitations of adaptation to habitat.Electronic supplementary materialThe online version of this article (10.1007/s00114-018-1560-2) contains supplementary material, which is available to authorized users.

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Spray forms of various chemical compounds including compounds of plant origin, molluscicides, and insecticides were tested in order to investigate their possibilities for reducing damage to young rape plants caused by the slug Arion lusitanicus Mabille, 1868. Among them, abamectin (0.2%), methiocarb (0.5%) and metaldehyde (1.0%) reduced damage to the plants, although metaldehyde remained active for only nine days. These three chemical compounds were not phytotoxic to rape plants, and none of them proved lethal to the slugs at the concentration used. The reduction in rape plant damage was obtained as a result of their deterrent and/or antifeedant action. The results indicate that abamectin has high potential usefulness in protecting winter rape seedlings from slugs.

Herbivorous slugs do significant damage to many species of crop plants. A laboratory study was conducted to determine the rate and extent of damage caused to 16 plant species by Arion vulgaris, Arion rufus, and Deroceras reticulatum. It was found, that levels of damage caused to young plants of Brassica napus, Sorghum bicolor, Vicia faba, and Sinapis alba by the slugs A. vulgaris, A. rufus, and D. reticulatum were similar, while levels of damage caused to the other studied plants by particular slug species differed significantly. Based on the results of the damage by the investigated slug species, plants were categorised as heavily or lightly damaged.

Arion vulgaris is one of the most important slug pests of crop plants, and is extremely hard to control. We assessed the effectiveness of a slug pellets containing iron phosphate, compared with methiocarb-and metaldehyde-based molluscicides, and of the parasitic nematode P. hermaphrodita contained in the commercial bioproduct Nemaslug. The effect of various doses of these substances and the nematode in reducing slug damage to Chinese cabbage plants was evaluated in laboratory experiments. A reduction in slug numbers and plant damage was obtained following application of the molluscicides, and a reduction in plant damage following application of P. hermaphrodita (immersion of plant roots in the nematode-containing liquid). The results are of great practical significance, because they show that it is possible to reduce the recommended dose of iron phosphate (5 g/m 2) by one half. Another important finding is that application of the nematode in the form of root immersion is more effective than spraying. The study demonstrates the usefulness of the nematode and of the iron phosphate molluscicide in protecting plants from A. vulgaris; this is of particular importance for crops on which the application of traditional molluscicides is not possible.