Limacus maculatus (Mollusca, Gastropoda, Limacidae) in the Northeast of the Russian Plain

In 2025, Limacus maculatus (Kaleniczenko, 1851) slugs were discovered within the city of Izhevsk, Udmurt
Republic. The specimens were found in a large ravine with a spruce forest and a meadow. This record represents the
northeasternmost known population of L. maculatus on the Russian Plain. The colonization of this semi-natural biotope
underscores the species' high adaptive potential and indicates a capacity for further range expansion. This finding
demonstrates that L. maculatus successfully overwinters even in northeastern Europe and can colonize both forest and
meadow habitats. To date, known populations of L. maculatus in cities across the Russian Plain have been confined to
anthropogenic shelters such as greenhouses, conservatories, and building basements. Consequently, the species has been
classified as a domestizoid, i.e. a species restricted to human-made structures. The discovery of a population of L. maculatus
in a minimally disturbed spruce forest within an extensive urban ravine fundamentally alters the author’s perception of its
dispersal capabilities. It is evident that the species' naturalization in the natural and semi-natural forests and meadows across
many regions of the Russian Plain is merely a matter of time. Therefore, based on this evidence, L. maculatus should be
reclassified as an epecozoid – a species that has successfully colonized anthropogenic biotopes and continues to expand its
range into new habitats. This case exemplifies not only the invasion of an alien species but also a dynamic shift in its
ecological status within biogeocenoses. The research conducted under both field and laboratory conditions revealed notable
variability in the coloration of adult and juvenile L. maculatus. The general body color ranges from brownish-black to
lighter brown, adorned with irregular spots and sinuous, light-brown lines. The mantle exhibits a brown or dark olive color
with irregular olive spots. The reproductive system morphology is typical for the species. Egg clutches contain 31-32 eggs,
a characteristic number for the genus Limacus Lehmann, 1864. The eggs are connected by thin mucous filaments, forming
a distinct necklace-like structure. L. maculatus feeds on a wide range of vegetable and berry crops, marking it as potentially
dangerous agricultural pest. L. maculatus's ability to consume ruderal grasses and lichens ensures its survival and
persistence in anthropogenic biocenoses.