Montana Field Guide

A small slug, extended adults usually < 15 mm. Dorsal base color is light gray or tan, with pale blue flecking to varying density. Mantle is oval with irregular dark gray to brown spots, the head extending a short distance beyond the anterior margin. The tail is rounded dorsally, lacks a middorsal keel, but sports a series of shallow, parallel longitudinal and oblique grooves that appear as darker lines; lacking a line of abscission, present in the taildroppers (Prophysaon). The sole is undivided (not tripartite), mucous clear. The pneumostome is slightly posterior to the midline of the mantle on the right side (Leonard et al. 2003, Hendricks 2012, Burke 2013). Internal anatomy is described by Leonard et al. (2003).

Distinguished by a combination of extremely small size, unkeeled tail, sole of foot undivided (not tripartite), gray or tan color with blue flecking, dark spots on mantle, a series of dark gray or brown parallel and longitudinal grooves on the tail, and the absence of a line a abscission.

Mostly mesic mixed conifer forest and riparian woodlands, but typically moister than for some other slug species. Canopy species often include western redcedar, western hemlock, grand fir, Engelmann spruce, Douglas-fir, black cottonwood, paper birch, sometimes subalpine fir, western white pine, western larch, ponderosa pine, and lodgepole pine; secondary canopy includes alder, dogwood and western yew. Usually found relatively near perennial streams and seeps under woody debris, rocks, on moss mats, within leaf litter, sometimes within rotten logs (Hendricks 2012).

A captive individual laid eggs in mid-July that were near to hatching by mid September (Leonard et al. 2003).