Arion subfuscus group: Arion fuscus
Arion fuscus (Müller, 1774)
The Arion subfuscus group typical contains slugs that are fairly large, often attaining a maximum length of 70 mm as fully mature adults. A. subfuscus and A. fuscus were treated as the same species (A. subfuscus) until recently. They can be separated by molecular techniques as well as by internal morphological characters explained below. They range in color from grey-brown to orange brown and usually have dark brown bands running down the sides, laterally. The pneumostome is encircled by the stripe on the right side of the animal. Unlike others in this genus, individuals in the A. subfuscus group are rounded when contracted. The tubercles are minute and elongated, and the keel is absent. The foot fringe has vertical bands running its length. The sole of this group is dirty-white, and the mucus produced may either be yellow, orange and on rare occassions clear. Molecular techniques can also be used to identify members of this group.
The distinguishing morphological features of each species are:
Arion subfuscus (Draparnaud, 1805) - Genitalia large, light lavender in color and located on the margin of the digestive gland
Arion fuscus (Muller, 1774) - Genitalia small, dark in color and completely embedded in the digestive gland.
This pestifierous species can be found in a variety of habitats (e.g. forests, fields, gardens).
Anderson 2005; Beyer and Saari 1978; Grimm et al. 2009; Kantor et al. 2009; McDonnell et al. 2011; Pinceel et al. 2005