Krynickillus melanocephalus (Kaleniczenko, 1851) - Caucasian black-headed slug
For the first time, the species was recorded in Minsk in 2009, and in 2013 - in Vitebsk with a high level of population size, which indicates a previous period of naturalization in new territories. As for the neighboring countries, in Latvia the species was registered back in 1997, in the north of Ukraine (Kiev) - in 1998, European Russia (Tver, Moscow) - in 2011–2012. Distribution within Belarus is limited to large cities and urban agglomerations.
The Caucasian black-headed slug inhabits habitats with a sufficient level of moisture - gardens, parks and squares, areas along green hedges, lawns on moisture-retaining soils, flower beds, rabatki, garden plots, penetrates into forest parks and natural forests. Molluscs move mainly along the soil surface. The main food substrate in natural biotopes is leaf litter permeated with hyphae. They feed on juicy parts of plants (including vegetable and ornamental crops), fruit bodies of cap mushrooms, can consume carcasses of dead insects and molluscs, including their own species. During daylight hours, slugs hide in the litter, under stones and other shelters. TO.melanocephalus characterized by a one-year life cycle: in spring and summer, only young individuals emerging from overwintered eggs are found. Adult slugs appear in autumn (September – November) and die in winter. The activity of animals is observed at plus daytime temperatures until late autumn. It is a competitor to native slug species.
Typical injuries to slugs are abrasions, which are easily infected by microorganisms. Perceptibly damages a number of vegetable (cabbage, etc.) and ornamental (hosta, lily, etc.) crops, as well as products in vegetable stores and warehouses. For the fight, malacocides (molluscicides) are used, sprinkling surfaces with lime, dolomite flour, superphosphate.
The body is fusiform, smoothly pointed behind, with a blunt, often wavy keel, occupying about half of the back. The skin is comparatively thick. The wrinkles are large and convex, there are about 13–15 rows of wrinkles between the mantle gap and the middle line of the back. The color varies greatly: more often dirty-white, sometimes bluish-gray. Young specimens are lighter in color. With age, the back and mantle darken, turn gray or even brown, and the neck, head and tentacles become intensely black. The pigmentation of the neck extends to the part of the body covered by the hood. The right and left edges of the mantle, together with the pneumostomy ridge, the sides and sole, always remain light - light yellow or, more often, light gray, with a bluish tint. The body length of adults is about 40–45 mm (on average, 30–50 mm), the width is about 12 mm, and the length of the mantle is 20 mm. Individuals of this species differ well from the mesh slug, similar in size and common in Belarus (Derocerasreticulatum (Müller, 1774)) with a lighter body coloration, the absence of a reticular pattern, a darker coloration of the head and neck.