Montana Field Guide

A moderately large slug of about 50 mm extended, but may reach 60 mm or slightly larger. Dorsal base color varies from dark grayish-brown to reddish-brown or yellowish, a diamond-mesh furrow pattern on the foot, sometimes highlighted with dark pigment. The mantle is 1/3 to 2/5 the body length, is sometimes distinctly paler, and appears granular, with a pair of dark lateral bands. Head color similar to foot, but antennae often darker. Pneumostome is near the middle of the mantle in the anterior half, and on the right side. The tail is not keeled, although there may be a lighter mid-dorsal stripe in some individuals. The sole is undivided (not tripartite) and pale, with a line of abscission near the posterior quarter (sometimes distinct only under magnification); the mucous is yellow to orange, especially in disturbed animals. As the common name indicates, taildroppers have a line of abscission where the tail (end of the foot) can be dropped (autotomized), much as in lizards, as a defense against predator attack (Hendricks 2012, Burke 2013). Internal anatomy is described by Pilsbry (1948) and Forsyth (2004).

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; relatively sedentary.

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

Hermaphroditic, based on internal anatomy (Pilsbry 1948 and Forsyth 2004).

Habitat occupied by Prophysaon andersoni (low to moderate elevation mixed conifer forest, often in valley bottoms near water) is threatened by logging, grazing, fire, and possibly weed control and rural home development. The impact of fire retardant on this and other terrestrial mollusks is not known. Little is known about this species, including its sensitivity to disturbance.