Arion (Kobeltia) occultus Anderson, 2004
A. occultus was described in Ireland but is a recent non-native import, probably from W or SW Europe (Anderson 2004).
Emerge for wet, mild weather, and go into hiding for long periods. Build a hibernaculum (chamber shelter made of mucus and soil) when going into a period of inactivity (Anderson 2004).
Eggs laid on the soil surface. (Anderson 2004).
Arion distinctus, A. hortensis.
External: Yellow-brown body; a gray to dark gray band on each side, with white to yellow below the stripe and brown, gray, or black above the stripe; body forms a bell shape in cross-section when at rest; prominent, "keeled" dorsal tubercles, lighter than skin grooves in between; blue-gray tentacles; orange to yellow foot fringe without dark stripes or spots; 3-part sole, light yellow to sometimes orange in living animals, sole white when preserved; dark translucent central section of the sole (Anderson 2004).
Internal: Long, thin vas deferens; small epiphallus without bulbous apex and with papillate inner walls; no internal structure where epiphallus enters atrium; oviduct long with a thick basal part including two internal folds that form a ligula; spermatheca ovate with short, thick duct; spermatheca to far left of epiphallus; yellowish glandular tissue around upper oviduct; 2-part atrium with upper and lower sections; atrium without glandular covering; ~4.1mm long, simple cigar-shaped spermatophore with a short tail (Anderson 2004).
Distinguished from A. hortensis and A. distinctus: no bulbous apex of epiphallus, and no internal structure where epiphallus enters atrium; large oviduct; walls of atrium of A. occultus lack glandular tissue, spermatheca to far left of epiphallus. Similar to A. distinctus as adults (Anderson 2004).
Eggs: About 2.3 x 1.9 mm, light yellow; 30-50 eggs per clutch, 10-20 clutches of eggs laid (Anderson 2004).
Juveniles: Translucent at hatching and soon darken to adult colors (Anderson 2004).
30-42 mm long extended, 19-28 mm long at rest (Anderson 2004).
Native to: probably somewhere in W or SW Europe (Anderson 2004).
Non-native in: Northern Ireland (Co Down) (Anderson 2004).
Disturbed habitat; rests in soil in under rocks; is subterranean (Anderson 2004).
Mate in the spring and fall; in hiding October/November to March. Juveniles and adults coexist in populations at the same time (Anderson 2004). .
Dead and living plants (leaf litter, roots) eaten. Cereals eaten, fungus not eaten (Anderson 2004).