ISSN 1188-603X

No. 320 December 30, 2003 Victoria, B.C.
Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2


From: Robert G. Forsyth [ ]


This is the key to the species slug-like terrestrial molluscs of British Columbia, and it includes all confirmed species. Beyond the borders of the province, it will be of use in southeast Alaska, Alberta and adjacent parts of the Pacific Northwest. Care should be taken, however, when using this key in the latter region because additional native (and possibly exotic) species occur there.

Slugs are not a natural group within the molluscan class Gastropoda, but rather a grouping by convenience of animals with similar body form. Slugs are snails with the shell reduced and the viscera more or less incorporated into the tail (less so in Hemphillia for example). They usually have no external shell, but when there is one, the animal is incapable of retracting into it, as can snails.

The following key is derived from my book, Land Snails of British Columbia (Forsyth, in press). It differs from the keys in the book by combining the separate keys to genera and species into a single key and by eliminating internal anatomical features. Genital anatomy and to a lesser extent, anatomy of the gut, while important for recognition of genera, species, etc., have been omitted.

Until Land Snails of British Columbia (Forsyth in press) is published in spring 2004, there is no readily available guide to native slugs in British Columbia that is useful for non-specialists. Until then, there are currently two excellent English-language guides to European slugs (Cameron et al. 1983; Kerney & Cameron 1979). The monograph by Quick (1960), although nomenclaturally dated, has good summaries of the natural histories of European species. The paper by Rollo & Wellington (1975) on slugs of Vancouver and the Fraser Valley is also a little dated in its taxonomy of European slugs. The taxonomy of European slugs species (particularly within the genus Arion) have significantly been revised in recent years. In British Columbia, recent activity have brought forth unrecorded species of both native and exotic slugs, and the known ranges of many previously recorded species have been expanded.

Following the key is a glossary, an annotated list of species, and instructions for preserving slugs for scientific study.

Key to slugs

Note: Introduced European species are marked with an asterisk (*).

Animal with an exposed or partially exposed shell, either plate-like and mostly embedded within the mantle near the middle or front of the animal, or ear-shaped and at the tip of the tail - 2
Animal without a shell evident (either wholly internal, embedded under the mantle, or absent) - 5

Shell ear-shaped, at the tip of the tail - *Testacella haliotidea
Shell plate-like, mostly embedded in a well defined visceral hump located near the longitudinal middle of the animal - Hemphillia - 3

Animal small (length to ca 30 mm). Visceral pouch and mantle extending over ½ or more the length of the entire animal and with many small papillae - Hemphillia glandulosa
Animal larger (length to ca 60 mm). Visceral pouch and mantle extending less than ½ length of the entire animal and with a few scattered papillae only - 4

Caudal horn prominent - Hemphillia dromedarius
Caudal horn lacking - Hemphillia camelus

Animal very narrow and wormlike (length about 15× width when fully extended), pale greyish - *Boettgerilla pallens
Animal not as above - 6

Pneumostome at or in front of the midline of the mantle on the right side - 7
Pneumostome behind the midline of the mantle on the right side - 17

Tail often having an oblique constriction that marks the site of self-amputation; caudal mucus pore absent - Prophysaon - 8
Tail never without an oblique constriction; caudal mucus pore present - Arion - 11

Animal blue-grey, without lateral bands - Prophysaon coeruleum
Animal variously pigmented but not blue-grey and usually with bands - 9

Animal variable in colour, but generally with reddish pigment: red on the back, grey-buff at the sides, generally with two conspicuous lateral bands running back along the tail from the mantle, defining a wedge-shaped, lighter dorsal area which may enclose a dark dorsal stripe at midline - Prophysaon vanattae
Animal generally without reddish pigment. Lateral bands not prominent on tail. Back usually with a light dorsal stripe at midline - 10

Section of tail capable of being self-amputated relatively shorter (ca 1/3 the length of the body, from posterior edge of the mantle to the tip of the tail; foot fringe usually without dark vertical bars (but sometimes faint); body length of adults up to ca 60 mm - Prophysaon andersoni
Section of tail capable of being self-amputated relatively longer; foot fringe with usually dark vertical bars (but sometimes very faint); body length of adults up to ca 120 mm (but can be as small as ca 30 mm) - Prophysaon foliolatum

Length to about 15 mm, tubercles on the back having soft points, giving the contracted animals a "prickly" appearance; body yellowish grey with head darker and lateral bands usually faint - *Arion intermedius
Adults longer than 20 mm, without a "prickly" appearance when contracted; variously pigmented - 12

Contracted body not bell-shaped in cross-section; ground colour dark grey or bluish grey, sometimes with a brownish tinge - *Arion distinctus
Contracted body bell-shaped in cross-section; if less than bell-shaped, ground colour usually orange-yellow to brown - 13

Animal very large, greater than 70 mm in length (up to nearly 200 mm), tubercles very coarse; adults usually not banded; animals often exhibit a twisting, rocking motion when disturbed - *Arion rufus
Animal smaller, less than 70 mm in length; tubercles finer; usually banded; animals without rocking behaviour - 14

Body with ground colour of reddish brown, rusty orange or occasionally yellow; body mucus yellow or orange; slugs cannot contract into a hemispherical shape (viewed from the side) - *Arion subfuscus
Body with ground colour of light greyish or brownish grey or with yellowish on the body; body mucus colourless; slugs can contract into a hemispherical shape - 15

Body light grey with a yellowish or cream tinge and usually with a yellowish band below the lateral bands (mantle not dotted) - *Arion fasciatus
Body light grey, without the yellowish tinge or "zone" below the lateral bands - 16

Lateral bands more or less blurred below; mantle with dark dots. Distal third of the epiphallus heavily pigmented with dark dots - *Arion circumscriptus
Body pale grey, fading to white on the sides, lateral bands well contrasted on lower edge; mantle without dark dots. Epiphallus unpigmented or only very slightly pigmented - *Arion silvaticus

Mantle smooth or granular, without concentric folds or ridges - 18
Mantle with a pattern of concentric folds or fingerprint-like ridges - 19

Mantle very large, covering most of the dorsal surface of the animal; dorsal keel absent - Magnipelta mycophaga
Mantle not exceptionally large; dorsal keel well developed - Ariolimax columbianus

Tail gradually tapering to a point; mantle ridges centred on the midline; dorsal keel long (about ¼ of the length of the body) - 20
Tail obliquely truncated; mantle ridges centred on right side above the pneumostome; dorsal keel short - Deroceras - 22

Mantle usually with distinct dark lateral bands (but sometimes faint) - *Lehmannia valentiana
Mantle solid coloured, spotted or marbled, but without bands - 21

Body yellowish with grey mottling; tentacles bluish; body mucus yellowish - *Limacus flavus
Body greyish with darker mottling; tentacles reddish brown; body mucus colourless - *Limax maximus

Body mucus milky white when the animal is irritated; body colour cream or pale grey, usually with darker grey reticulation; animal 35-50 mm long - *Deroceras reticulatum
Body mucus always clear; body colour varies; animal * 35 mm - 23

Animal * 35 mm; body colour brown, often with darker spots and fine speckles - *Deroceras panormitanum
Animal smaller, * 25 mm; body colour varies and may be spotted - Deroceras hesperium and Deroceras laeve


Caudal horn
In Hemphillia, a fleshy protuberance at the end of the tail.
Foot fringe
The edge of the foot set off from the rest of the foot by a conspicuous constriction.
A ridge along the midline of the tail, which when present, is complete (extending the entire length) or incomplete (only at the hind end).
A fold of the body wall lining and secreting the shell in shell-bearing molluscs; it is exposed in slugs (the "shield") as a clearly demarked, raised area on the body of the slug, behind the head.
Visceral hump
The major conglomeration of organs forming much of the body. Papillae
A minute protuberance on the skin.
The hole on the right side of the mantle through which the animal breathes (breathing pore).
A netlike pattern.

Checklist of British Columbia slugs

Twenty-four species of slugs are known from British Columbia. Of these, 13 are introduced European species, marked here with an asterisk (*). For a complete list of introduced terrestrial molluscs (includes snails) and photos, see






A request for data

Gardeners, botanists and horticulturalist often have intimate knowledge slugs in gardens. I am always interested in receiving records of exotic and native slugs in British Columbia. In particular, among the exotic species, all records of Testacella haliotidea, Boettgerilla pallens, Limacus flavus and Arion silvaticus, or species not included here, are of interest. Records of most species of exotic slugs from areas outside of southern Vancouver Island and Greater Vancouver are especially useful as well, since there are relatively few records from elsewhere. For further information, please contact me:

Preserving slugs

Preserving slugs for dissection and museum collections is relatively easy. Slugs dropped directly into alcohol will twist and contract and produce large quantities of mucus, so this should be avoided. Most sluggers advocate drowning in water, usually overnight, to relax the animal, but the longer the slug stays in water, the greater the chance of decomposition starting-and it is not so kind for the slug. I use carbonated water, namely Perrier, which drowns slugs much quicker. Once relaxed (dead), slugs can be transferred to 70% ethanol (EtOH). Isopropyl alcohol (rubbing alcohol in drug stores) is cheap and easily found, and can be used in a pinch, but it overly hardens tissues. Rubbing compound (mostly ethanol, plus extra stuff to make it unpalatable) can usually also be found in drugstores, and once diluted to 70% works as good as the real thing. As water is drawn out of the tissue, the fluid should be changed.


Cameron, R.A.D., B. Eversham, & N. Jackson. 1983.
A field key to the slugs of the British Isles. Field Studies 5:807-824.
Davies, S.M. 1977.
The Arion hortensis complex, with notes on A. intermedius Normand (Pulmonata: Arionidae). Journal of Conchology 29:173-187.
Davies, S.M. 1979.
Segregates of the Arion hortensis complex (Pulmonata: Arionidae), with the description of a new species, Arion owenii. Journal of Conchology 30:123-127.
Forsyth, R.G. In press.
Land Snails of British Columbia. Royal British Columbia Museum/UBC Press.
Kerney, M.P., & R.A.D. Cameron. 1979.
A field guide to the land snails of Britain and north-west Europe. London: Collins.
Quick, H.E. 1960.
British slugs (Pulmonata; Testacellidae, Arionidae, Limacidae). Bulletin of the British Museum (Natural History), Zoology 6 (3):103-226.
Rollo, C.D., & W.G. Wellington. 1975.
Terrestrial slugs in the vicinity of Vancouver, British Columbia. The Nautilus 89:107-115.
Wiktor, A. 2000.
Agriolimacidae (Gastropoda: Pulmonata) - a systematic monograph. Annales Zoologici (Museum and Institute of Zoology, Polish Academy of Sciences) 49:347-590.

Robert G. Forsyth []
Research Associate
Royal British Columbia Museum
675 Belleville Street, Victoria, BC
Canada V8W 9W2
Mailing address: PO Box 3804, Smithers, BC, Canada V0J 2N0


From: Mark Fraker []

Deer overabundance has reached extreme proportions in many areas of North America. Consequences include hazards to traffic, habitat degradation, and disease transmission. Where hunting is not practical or permissible, people have sought non-lethal means. The most promising approach is immunocontraception (IC). IC exploits the fact that the glycoproteins in the outer layer of the mammalian egg, the zona pellucida, are involved in sperm-binding. For more than a decade, scientists have experimented with using porcine zona pellucida (PZP) proteins as the antigens in vaccines. The PZP elicits antibodies that bind to the surface of the eggs of the treated female mammal. For certain groups, such as deer and horses, the vaccines can be very effective. Practical application of IC to control populations of overabundant deer requires that a large proportion (80%) of the population be treated and reducing populations by IC alone can take several years. To achieve control more quickly and economically, a combination of IC and lethal removal can be applied. PZP vaccines have no potential for adverse food-chain effects. The vaccines are entirely biodegradable, as are the antibodies that are produced by the treated deer. A number of studies have shown that PZP vaccines are safe for the treated animals, as well. Most PZP vaccines require a booster inoculation in the first year and annual boosters thereafter. Because accessing the deer for treatment is very costly, vaccines that require boosting are not practical or economic. The exception to this is SpayVac(tm), which has proven to be 100% effective for 3 years in both Fallow Deer and White-tailed Deer. At the end of 3 years, the antibody titers remained high, so that contraception will likely continue indefinitely. (The Fallow Deer research results are reported in: Fraker, M.A. et al. 2003. Long-lasting, single-dose immunocontraception of feral fallow deer in British Columbia. Journal of Wildlife Mangement 66(4):1141-1147.) For more information about SpayVac(tm) and immunocontraception, you can visit the SpayVac(tm) website at, or contact Mark Fraker at .


From: Douglas A. Landis, Corresponding author: []
Douglas A. Landis, Donald C. Sebolt, Michael J. Haas, & Michael Klepinger. 2003.
Establishment and impact of Galerucella calmariensis L. (Coleoptera: Chrysomelidae) on Lythrum salicaria L. and associated plant communities in Michigan. Biological Control 28: 78-91. Abstract.

Purple loosestrife, Lythrum salicaria L. (Lythraceae) is an invasive wetland perennial plant of Eurasian origin that is widely established in North America and is considered a threat to native wetland flora and fauna. Two European beetles, Galerucella calmariensis L. and Galerucella pusilla Duft. (Coleoptera: Chrysomelidae) have been introduced and widely distributed in North America for biological control of Lythrum salicaria. Experimental releases of Galerucella spp. beetles were made in three locations in Michigan in 1994. In 1997 we initiated a project to rear, redistribute, and evaluate the impacts of Galerucella calmariensis in 19 additional sites throughout Michigan. G. calmariensis became established at 100% of the 24 release locations monitored in these studies and have persisted for up to seven years while G. pusilla apparently failed to establish. Large populations of G. calmariensis developed from each of the 1994 releases and caused 100% defoliation of L. salicaria. From 1995 to 2000, L. salicaria stem height was reduced 73-85%, percent plant cover was reduced 61-95%, and richness of nontarget plant species increased significantly at four out of five sites. By 2001, L. salicaria stem height and percent cover were reduced 38-81% and 32-74%, respectively, and nontarget plant species richness increased significantly at all five sites in contrast to the situation in 1995. Beetles have spread 3-10 km from these original release sites. Of the 19 additional sites monitored for 3-5 years post-release, 50% (4/8) of the 1997 releases have developed into large G. calmariensis populations and produced severe damage to L. salicaria. Thirty-three percent (2/6) of the 1998 releases have generated moderate impacts while all 1999 releases (5/5) remain without clear impacts. The successful establishment, spread, and impacts of G. calmariensis indicate the critical need for additional research on its role in the restoration of desirable plant communities in areas formerly dominated by L. salicaria.


From: Cambridge University Press []
Zabel, Cynthia J. & Robert G. Anthony (eds.) 2003.
Mammal Community Dynamics Management and Conservation in the Coniferous Forests of Western North America. Cambridge University Press, New York. 732 p. ISBN 0-521-00865-4 [soft cover] Price: US$60.00

Order from: Cambridge University Press, 100 Brook Hill Drive, West Nyack, NY 10994-2133, USA Phone: 845-353-7500, fax: 845-353-4141

This book provides a synthesis of the literature on the role of forest mammals in community structure and function in the coniferous forests of western North America, with emphasis on management and conservation. In addition to coverage of some of the charismatic megafauna such as grizzly bears, gray wolves, mountain lions, elk and moose, the book also includes thorough treatment of small terrestrial mammals, arboreal rodents, bats, medium-sized carnivores, and ungulates. The unique blend of theoretical and practical concepts makes this book equally suitable for managers, educators, and research biologists.


Foreword Jack Ward Thomas

Part I. Management and Conservation Issues for Various Taxa:

  1. Introduction and historical perspective C. Zabel and R. Anthony
  2. Forests and woodlands of western North America M. Hemstrom
  3. Faunal composition and distribution of mammals in western coniferous forests T. Lawlor
  4. Habitat ecology and conservation of bats in western coniferous forests J. Hayes
  5. Ecological relationships of terrestrial small mammals in western coniferous forests J. Hallet, M. O' Connell and C. Maguire
  6. Ecology and conservation of arboreal rodents of western coniferous forests W. Smith, J. Waters, R. Anthony, N. Dodd and C. Zabel
  7. Small and mid-sized carnivores S. Buskirk and W. Zielinski
  8. Ecology, conservation and restoration of large carnivores in western N. America K. Kunkel
  9. Ungulates in western coniferous forests: habitat relationships, population dynamics and ecosystem processes J. Kie, R. Terry Bowyer and K. Stewart

Part II. Community and Ecosystem Relations:

  1. Relationships among fungi and small mammals in forested ecosystems D. Luoma, J. Trappe, A. Claridge, K. Jacobs and E. Cazares
  2. Ecology of coarse woody debris and its role as habitat for mammals W. McComb
  3. The ecological role of tree-dwelling mammals in western coniferous forests K. Aubry, J. Hayes, B. Biswell and B. Marcot
  4. The role of ungulates and large predators on plants, community structure and ecosystem processes in national parks F. Singer, G. Wang, and N. Hobbs
  5. The role of the lynx-hare cycle in boreal forest community dynamics S. Boutin, C. Krebs, R. Boonstra and A. Sinclaire
  6. Association of mammals with riparian ecosystems in Pacific Northwest forests R. Anthony, A. O'Connell, M. Pollock and J. Hallet

Part III. Conservation Issues and Strategies:

  1. Small mammals in a landscape mosaic: implications for conservation K. Martin and W. McComb
  2. Measuring and interpreting changes in connectivity for mammals in coniferous forests L. Scott Mills, M. Schwartz, D. Tallmon, K. Lair
  3. An evolutionary and behavioural perspective on dispersal and colonization of mammals in framented landscapes J. Wolff
  4. The functional diversity of mammals in coniferous forests of western North America B. Marcot and K. Aubry
  5. Synthesis and future perspective R. Anthony and C. Zabel



I have been running the so-called Botany Nights for the Victoria Natural History Society, and one of the most successful Botany Night was Robert Forsyth's workshop on identification of slugs! I hope that you will appreciate his key to slugs the same way the Botany Night's participants appreciated his workshop. Birth control of deer may be a solution of managing deer populations in urban areas, chrysomelid beetles are used to control purple loosestrife in North America, and a book announcement on West Coast mammals wraps up this issue of ZEN, excuse me, BEN, quite well. Nevertheless, I promise that the next issue of BEN will be BEN again.

All the best in the year 2004!

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