Deroceras (Deroceras) praecox Wiktor, 1966
External: Slug white, sometimes creamy, covered by rare dark brown or red-brown or dark brown spots (no reticulate pattern); mucus colourless, milky white when irritated.
Internal: Penis divided in two parts, anterior part broad, posterior part narrower and elongated with a helically coiled apppendix at penis apex, which is usually unilaterally dark-pigmented; penial gland consists of 3-4 long processes set on a common trunk, attached to penis at the base of appendix; penial retractor muscle's main part inserts laterally at the base of appendix, and has a thinner strand running to the anterior part of the penis, attaching there; stimulator very flat, fan-shaped; rectal caecum in the form of a shallow pocket.
Differs from the very similar D. rodnae: paler and has larger spots; spirally coiled appendix; bifurcated penis rectrator muscle.
Up to 40 mm long (preserved 35 mm).
S Poland (Carpathian and Sudete mountains, lowland as far as Kraków-Wieluń Jura and Lower Silesia lowlands), Czech Republic, Slovakia, W Ukraine (Sysoev & Schileyko 2009).
Type Locality: Poland: Lower Silesia, Opawskie mountains, Pokrzywna.
Sympatric with D. rodnae only in Slovakia. .
Deciduous and mixed forests; up to 1200 m altitude; prefers shady and humid habitats, near springs and streams; on low plants and mosses, very rarely under wood; crawls on the undergrowth vegetation and shelters in soil and leaf litter. Occurs in low numbers.
Adults occur almost exclusively between April and June, later than in D. rodnae.