Well, it's a learning process. It appears my first instinct was correct in the identification of my philomycid slug I affectionately refer to as Zoidberg-- it is a Philomycus togatus (Toga Mantleslug). I have observed the animal for a week or so now and realize that the foot sidewall always has a pinkish orange hue. In the field I guess the lighting made me think it was paler. Also the mucus color of orange is diagnostic as the only known philomycid with orange mucus is the Toga Mantleslug.
I can't find the reference where I read that P. togatus is the only Philomycid known to have orange mucus but I will update this post when I refind that quotation.
From H.L. Fairbanks' The Taxonomic Status of Philomycus Togatus (Pulmonata: Philomycidae): A Morphological and Electrophoretic Comparison with Philomycus Caolinianus (Malacologia, Vol. 27, No1, 1986):
"Among the species of Philomycus only P. rushi Clapp, 1920, a small (15-20mm) slug, has been described as having orange or red in the sides of the foot. Pilsbry (1948) synonymized P. rushi with Palifera ohioensis (Sterki). There are two large Palifera (P. varia and P. ragsdalei) with red or orange in the foot margins. However, Philomycus togatus has a dart sac and dart and therefore must remain in the genus Philomycus. This makes it the only know species in the genus recorded as having orange foot margins."
Interestingly I also now possess a P. carolinensis/ P. flexuolaris and the mucus is a milky white but it's very hard to see a difference in mantle pattern. Both individuals are heavily mottled but with the P. togatus I can make out lateral stripes on both sides. On the other I can just barely make out darker spots of dark brown/black on the back as two close lines leaving me still dumbfounded as to it's identification as either P. carolinensis or P. flexuolaris. If I went based on likelihood of know distribution I'd guess P. flexuolaris, especially since it was collected up here in the mountains in the northeastern portion of our state. Eventually I'll post photos and hopefully a definitive identification.
|Range map from Land Snails of Limestone Communities and Update of Land Snail Distributions in Pennsylvania (Pearce) with my own county added to range (in orange). Formerly unknown to Luzerne County.|