Montana Field Guide

A moderately large slug of about 50 mm extended, but may reach 70 mm or slightly larger. Dorsal base color pale orange or reddish-yellow to tan, the foot with a series of oblique furrows and reticulations sometimes highlighted with dark pigment. The mantle is 1/3 to 2/5 the body length, sometimes distinctly paler than the foot and with a granular appearance, with a pair of dark lateral stripes that meet along the posterior margin, mantle sometimes also with several indistinct grayish splotches. Head color is like the mantle, the tentacles darker. The pneumostome is near the middle of the mantle in the anterior half, and on the right side. There is a lighter-colored broad mid-dorsal band on the tail bounded by a pair of wide gray to dark brown bands reaching to the tip of the tail and appearing somewhat as extensions of the mantle stripes; the tail is not keeled. The sole is undivided (not tripartite) and pale, with a line of abscission near the posterior fifth of the foot (sometimes distinct only under magnification); the mucous is yellow to orange, especially in disturbed animals (Hendricks 2012, Burke 2013). Internal anatomy is described by Pilsbry (1948).

Unlike other Montana slugs except the congeneric Smoky Taildropper. Dorsal surface of the Reticulate Taildropper has a distinct diamond-like mesh pattern of dark furrows. Smoky Taildropper has an indisctinct diamond-mesh pattern on the tail, but has a broad mid-dorsal stripe that is bounded by darker bands (lacking on the Reticulate Taildropper).

No information.

Mostly in mesic mixed conifer forest, often relatively close to water. Canopy species include western redcedar, western hemlock, grand fir, Douglas-fir, Engelmann spruce, subalpine fir, ponderosa pine, black cottonwood, paper birch, aspen, western larch, and lodgepole pine, with secondary canopy sometimes including alder, dogwood, willow, Pacific yew, and hawthorn. Usually found under woody debris and leaf litter or in downed rotten wood, sometimes under rocks (Hendricks 2012).

No information.

The posterior part of the foot can be dropped (autotomized), much as in lizards, as a defense against predator attack; small individuals sometimes drop their tails while being held in-hand, and the dropped tails may continue to wiggle for over an hour (Hendricks 2012).

Hermaphroditic, based on internal anatomy (Pilsbry 1948).

Habitat occupied by Prophysaon humile (moist sites in moderate elevation mixed conifer forest, often in valley bottoms) is threatened by logging, mining, fire, and rural home development, and possibly weed control (Frest and Johannes 1995). The impact of fire retardant and herbicides on this species and other terrestrial mollusks is unknown. Little is known about the biology of this species, including its sensitivity to disturbance.