Name that slug: slug taxonomy
Slugs are mollusks in the phylum Mollusca. The information below highlights the taxonomy of slugs of economic interest as pest species.
Class GASTROPODA
Subclass Gymnomorpha
Order SOLEOLIFERA
Family Veronicellidae (=Vaginulidae)
The mantle of Veronicellid slugs covers the entire surface dorsal surface of the animal. Veronicellid slugs include several species of slugs found in the genera Vaginulus and Veronicella. They are herbivores and live mainly in tropical and subtropical Africa, America and Asia. They are also intermediate hosts of Angiostrongylus costaricensis, the rat lung worm.
Subclass Pulmonata
Order STYLOMMATOPHORA
Suborder Sigmurethra
The families:
Testacellidae
These are an earthworm's enemy, a carnivore with sharp teeth that impale their wormy prey. The remnant of a shell at the tail end of the slug covers the mantle and organs. This family is comprised of a single genus, Testacella. Testacella has been introduced into North America and New Zealand. Regionally, Testacella sp. has been found in the Portland and Eugene areas of Oregon.
Testacella haliotidea
Photo: Claudia Groth
Urocyclidae
Parmacellidae
Milacidae
The pneumostome is located posterior to the midpoint of the mantle. A dorsal key is present. There is no caudal mucous gland.
Limacidae
The pneumostome is located posterior to the midpoint of the mantle. A dorsal keel is present. There is no caudal mucous gland. This family includes several large slug species in the genus Limax. Limax maximus is very prominent in the Pacific Northwest and also been distributed in other regions of North America. Limax flavus, also called the cellar slug, can also be found in the northwest. It can be recognized by its brilliant blue tentacles.
Limax maximus
Photo: Rosetta
This family also includes the genus Deroceras. This genus includes several species that can reach pest status including: D. agreste, D. laeve, the marsh slug, D. reticulatum, the field slug or milky slug.
Deroceras reticulatum
Photos: Rosetta, Oregon State University
Lehmannia valentiana can also be found in the Pacific Northwest. The mantle has dark lateral bands and dark bands along the dorsal side of the foot.
Photo: Rosetta
Boettgerillidae
Trigonochlamydidae
Arionidae
This family of slugs has a mantle on the front part of the slug body. The pneumostome is located towards the anterior portion of the mantle. Subfamilies of arionid slugs are separated by anatomical features.
Ariolimacinae
This subfamily includes the well known genera of banana slug, Ariolimax columbianus (Gould); A. dolichophallus; and A. californicus. Slugs in this subfamily have a keel along their back. They can often be found with a slime plug or caudal pore with a mucous plug. 
Photo: Rosetta
Anadeninae
The subfamily has a number of genera found in North America. The genus Prophysaon andersoni (Cooper) is endemic in the Pacific Northwest. This species can drop a portion of its foot as a defensive measure giving it the common name, the reticulate taildropper. The pneumostome is located near the middle of the mantle.
Arioninae
The subfamily contains several genera commonly found in the Pacific Northwest, although exotic transplants. These slugs can be quite large. There may be a prominent fringe along the edge of their foot. The pneumostome is located towards the front of the mantle, anterior to the midpoint. These slugs also have a well developed caudal mucous gland. One of key genera in this subfamily is Arion. A. rufus, A. ater, A. circumcriptus, Arion subfuscus are some of the species commonly found in the Pacific Northwest. These mostly palaearctic slugs have been distributed worldwide including in America, Australia, New Zealand, and South Africa.
Arion subfuscus can eat a wide variety of foods but fungi and decaying vegetation have been noted as their preferred diet. This species has a flexible abilty to occupy a variety of ecological environments (Beyer and Saari, 1978).
Arion rufus
Photo: Rosetta
Arion species, possibly A. subfuscus
, known as the dusky slug.
Photo: Rosetta
Philomycidae
References:
N. Beyer and D. Saari. 1978. Activity and Ecological Distribution of the Slug, Arion subfuscus (Drapanard) (Stylommatophora, Arionidae). American Midland Naturalist.
Page last modified 5/17/13