Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Arion vulgaris
(Spanish slug)



Arion vulgaris (Spanish slug)


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Egg mass of A. vulgaris in soil.
CaptionEgg mass of A. vulgaris in soil.
CopyrightB. Speiser/FiBL Switzerland
Egg mass of A. vulgaris in soil.
OvaEgg mass of A. vulgaris in soil.B. Speiser/FiBL Switzerland
Two differently coloured juvenile A. vulgaris. Note the dark lateral bands on the slugs.
TitleColour morphs
CaptionTwo differently coloured juvenile A. vulgaris. Note the dark lateral bands on the slugs.
CopyrightB. Speiser/FiBL Switzerland
Two differently coloured juvenile A. vulgaris. Note the dark lateral bands on the slugs.
Colour morphsTwo differently coloured juvenile A. vulgaris. Note the dark lateral bands on the slugs.B. Speiser/FiBL Switzerland
Adult A. vulgaris in copula.
CaptionAdult A. vulgaris in copula.
CopyrightB. Speiser/FiBL Switzerland
Adult A. vulgaris in copula.
AdultAdult A. vulgaris in copula.B. Speiser/FiBL Switzerland
Adult A. vulgaris fully extended.
CaptionAdult A. vulgaris fully extended.
CopyrightB. Speiser/FiBL Switzerland
Adult A. vulgaris fully extended.
AdultAdult A. vulgaris fully extended.B. Speiser/FiBL Switzerland
Lettuce damaged by A. vulgaris (a) and undamaged (b).
TitleField damage
CaptionLettuce damaged by A. vulgaris (a) and undamaged (b).
CopyrightB. Speiser/FiBL Switzerland
Lettuce damaged by A. vulgaris (a) and undamaged (b).
Field damageLettuce damaged by A. vulgaris (a) and undamaged (b).B. Speiser/FiBL Switzerland
Bean plant damaged by A. vulgaris.
TitleField damage
CaptionBean plant damaged by A. vulgaris.
CopyrightB. Speiser/FiBL Switzerland
Bean plant damaged by A. vulgaris.
Field damageBean plant damaged by A. vulgaris.B. Speiser/FiBL Switzerland
Pumpkin damaged by A. vulgaris. Note extensive damage (arrowed) to pumpkin skin and additional damage to stalk.
TitleField damage
CaptionPumpkin damaged by A. vulgaris. Note extensive damage (arrowed) to pumpkin skin and additional damage to stalk.
CopyrightB. Speiser/FiBL Switzerland
Pumpkin damaged by A. vulgaris. Note extensive damage (arrowed) to pumpkin skin and additional damage to stalk.
Field damagePumpkin damaged by A. vulgaris. Note extensive damage (arrowed) to pumpkin skin and additional damage to stalk.B. Speiser/FiBL Switzerland
Juvenile of pale phase.  Starcross, England.
CaptionJuvenile of pale phase. Starcross, England.
CopyrightRoy Anderson
Juvenile of pale phase.  Starcross, England.
JuvenileJuvenile of pale phase. Starcross, England.Roy Anderson
Brown and black variant of dark phase.  Antrim, Co. Antrim, Ireland.
TitleBrown and black variants
CaptionBrown and black variant of dark phase. Antrim, Co. Antrim, Ireland.
CopyrightRoy Anderson
Brown and black variant of dark phase.  Antrim, Co. Antrim, Ireland.
Brown and black variantsBrown and black variant of dark phase. Antrim, Co. Antrim, Ireland.Roy Anderson
Juvenile of dark phase. Honau, Germany.
CaptionJuvenile of dark phase. Honau, Germany.
CopyrightRoy Anderson
Juvenile of dark phase. Honau, Germany.
JuvenileJuvenile of dark phase. Honau, Germany.Roy Anderson
Red form of dark phase, in copula. Note dark underlying pigment in pneuostome (arrowed).  Honau, Schwäbiacher Alb, Germany.
TitleRed form
CaptionRed form of dark phase, in copula. Note dark underlying pigment in pneuostome (arrowed). Honau, Schwäbiacher Alb, Germany.
CopyrightRoy Anderson
Red form of dark phase, in copula. Note dark underlying pigment in pneuostome (arrowed).  Honau, Schwäbiacher Alb, Germany.
Red formRed form of dark phase, in copula. Note dark underlying pigment in pneuostome (arrowed). Honau, Schwäbiacher Alb, Germany.Roy Anderson
Pale phase in copula.  Starcross, Devon, England.
TitlePale phase
CaptionPale phase in copula. Starcross, Devon, England.
CopyrightRoy Anderson
Pale phase in copula.  Starcross, Devon, England.
Pale phasePale phase in copula. Starcross, Devon, England.Roy Anderson


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Preferred Scientific Name

  • Arion vulgaris Moquin-Tandon 1855

Preferred Common Name

  • Spanish slug

Other Scientific Names

  • Arion lusitanicus Mabille 1868

International Common Names

  • Spanish: babosa lusitana
  • French: arion rouge; limace ibérique; limace noire; limace rouge

Local Common Names

  • Germany: Spanische Wegschnecke

EPPO code

  • ARIOLU (Arion lusitanicus)

Summary of Invasiveness

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The invasiveness of A. vulgaris is related to several factors. Its ability and readiness to colonize humanly-disturbed environments is of major importance. Proschwitz (1997) observed that 99% of Swedish records were from synanthropic habitats and only 1% from natural woodlands. With a proximity to humans, comes the possibility of passive dispersal through trade, particularly in living plants. The garden centre trade and horticulture are particularly implicated (Weidema, 2006). In Poland, there is evidence from studies of molecular diversity that A. vulgaris has originated from repeated, separate introductions from other parts of Europe (Soroka et al., 2007). 

The ability of A. vulgaris to utilize a great variety of food sources and types has been well-documented and must aid dispersal and colonization. 

Other than its country of origin (France), it is considered to be invasive across western and central Europe, from the Pyrenees to eastern Poland and from southern France to north Italy, Austria and Slovakia and within an isolated range in eastern Bulgaria.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Mollusca
  •             Class: Gastropoda
  •                 Subclass: Pulmonata
  •                     Order: Stylommatophora
  •                         Suborder: Sigmurethra
  •                             Unknown: Arionoidea
  •                                 Family: Arionidae
  •                                     Genus: Arion
  •                                         Species: Arion vulgaris

Notes on Taxonomy and Nomenclature

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This species is best known as the Lusitanian slug Arion lusitanicus J Mabille 1868. However, the name lusitanicus can no longer be applied. A re-description of lusitanicus sensu Mabille, based on topotypes from its type locality at Setubal, Serra da Arrábida, Portugal (Castillejo, 1997, 1998) has shown that Portuguese lusitanicus has a very different spermatophore and internal morphology from the central and west European species to which this name was applied by Altena (1956) and then by subsequent authors. The distinction between topotypic Arion lusitanicus and Arion ‘lusitanicus’ from north-west Europe has been confirmed by phylogenetic analysis (molecular studies) through ITS1 sequencing (Quinteiro et al., 2005; Colomba et al., 2007). Falkner et al. (2002) proposed that the pest species in north-west Europe is called vulgaris Moquin-Tandon, 1855 as this appears to be the first available name that can be unambiguously applied. This is possible because Moquin-Tandon (1855), unusually among early authors, figured the highly diagnostic spermatophore in his description.

British authors, including Quick (1960), have confused vulgaris with Arion flagellus Collinge, a large Arion that inhabits the British Isles and northern Iberia, but has not so far been found elsewhere in Europe nor further afield. Some of Quick’s drawings of ‘lusitanicus’, particularly of the spermatophore (p. 142), actually relate to flagellus. This has clearly been a source of confusion and the reader is directed to Davies’ (1987) paper that first resolved the problem and gives a very detailed account of the distinguishing features and reproductive biology of flagellus and vulgaris (as lusitanicus).


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Pneumostome located on the right-hand side of the mantle and near the front margin; keel absent; mantle granular. Foot fringe broad, heavily lineolated, similar in colour to that of the back. Juveniles have dark lateral bands with paler ‘shadow’ bands on the sides above these – compare juvenile Arion rufus and juvenile and adult Arion subfuscus. Sides below the bands are pale. Colour is variable - yellowish, greyish, chocolate, reddish, brownish (never greenish). The adults are normally unbanded, colour of the upper surface a uniform yellowish-brown, brown, reddish-brown or dark-brown, rarely black. Eggs are white, slightly transparent, soft-shelled, ca 2 mm in diameter. 

Hatchlings are ca 5 mm long when stretched out. The adults are 6-12 cm long and normally weigh 5-15 g (extremes: 3-27 g) (Briner and Frank, 1998).


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Moquin-Tandon’s description of A. vulgaris relates to a species inhabiting southern France (Moquin-Tandon, 1855). Arion lusitanicus sensu Mabille, on the contrary, is restricted to Portugal (Quinteiro et al., 2005). In addition, there is no evidence to suggest that vulgaris occurs on the Iberian peninsula outside the southern Pyrenees of Catalunya (Chevallier, 1981; Castillejo, 1998; Quinteiro et al., 2005). Theories for its area of origin range from southern Europe (Schmid, 1970) to the Alpine Region (SM Davies, [address available from CABI], personal communication, undated). Chevallier (1981) gives a map showing its French range, which is mainly Pyrenean rather than alpine.

A. vulgaris has been spread by international trade from central and south France, and can now be found throughout much of central, northern and eastern Europe. In many regions it is well-established and has partly replaced the native large arionids: Arion rufus and Arion ater, especially in anthropogenic habitats, to become a serious pest (Fechter and Falkner, 1990; Turner et al., 1998). It appears to be uncommon at higher altitudes, at least in the Alps (ca. 1600 m above sea level) (Turner et al., 1998) although this may not apply to the Pyrenees (Chevallier, 1981).

Extensions in its range have been recorded in a number of countries since 2000. It is now confirmed from Ireland (Anderson, 2010), where it was earlier confused with other taxa. It has recently been found in Iceland for the first time. There is a single unconfirmed report from Cornell University in the USA (October 1998).


Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

South America

Falkland IslandsUnconfirmed record1986Introduced Invasive Proschwitz TVon, 1988In Stanley, Probably this species, but unconfirmed


AndorraPresentIntroducedCesari, 1978
AustriaWidespreadIntroduced1972 Invasive Fischer and Reischütz, 1998
BelgiumWidespreadIntroduced1974 Invasive De Winter, 1989
BulgariaLocalisedIntroduced Invasive Kerney et al., 1979; Wiktor, 1983Synanthropic; Stara Planina only
Czech RepublicWidespreadIntroduced1993 Invasive Dvorák and Horsák, 2003; Stranc et al., 2006
DenmarkWidespreadIntroduced1991 Invasive Proschwitz and Winge, 1994; Proschwitz TVon, 1997
Faroe IslandsWidespreadIntroduced1996 Invasive Weidema, 2006
FinlandLocalisedIntroduced Invasive Valovirta, 1995Aland Isles
FranceWidespreadNative Invasive Moquin-Tandon, 1855; Kerney et al., 1979; Chevallier, 1981Described from near Lyons in 1855, now widespread
GermanyWidespreadIntroduced1965 Invasive Schmid, 1970; Kerney et al., 1979; von Proschwitz, 1997; Ludwig et al., 2015
IcelandLocalisedIntroduced2003 Invasive Ingimarsdóttir and Ólafsson, 2005South only
IrelandPresentIntroduced Invasive Anderson, 2010
ItalyLocalisedIntroduced Invasive Cesari, 1978North only
LiechtensteinPresentIntroducedCesari, 1978
NetherlandsWidespreadIntroduced1988 Invasive De Winter, 1989
NorwayLocalisedIntroduced1988 Invasive Proschwitz and Winge, 1994; von Proschwitz, 1997Coastal; south and west
PolandWidespreadIntroduced1987 Invasive Koz<l>owski, 2007
-AzoresWidespreadBackhuys, 1975Unclear whether the taxon referred to here is vulgaris or lusitanicus s.s.
SlovakiaWidespreadIntroduced1992 Invasive von Proschwitz, 1997; Cejka et al., 2006
SloveniaPresentLaznik et al., 2010
SpainLocalisedNativeChevallier, 1981Catalunya only
SwedenWidespreadIntroduced1975 Invasive Proschwitz TVon, 1989; Proschwitz TVon, 1997
SwitzerlandWidespreadIntroduced1955 Invasive Turner et al., 1998
UKWidespreadIntroduced1954 Invasive Davies, 1987; Kerney, 1999

History of Introduction and Spread

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In the modern era, A. vulgaris was first recognised in the UK and France in the early 1950s (Winter, 1989; Kerney, 1999), in Switzerland in 1955 (Turner et al., 1998), in Germany in 1965 (Schmid, 1970 cited in Briner and Frank, 1998), in Belgium in 1974 (Winter, 1989), in the Netherlands in 1988 (Winter, 1989) and in Austria in 1972 (Fischer and Reischütz, 1998). Before German unification in 1990, A. vulgaris was well-established in West, but not in East Germany (von Proschwitz, 1997). The first record for the former East Germany is from 1994 (von Proschwitz, 1997). In Sweden, A. vulgaris was first recorded in 1975, but from 1987 onwards populations exploded and the species spread rapidly to new sites. Of all the records in Sweden, 99% are from anthropogenic and only 1% from natural woodlands (Proschwitz, 1997). 

Outside Europe, there is a suspected occurrence in the Falkland Islands (Proschwitz, 1988). This report has not been confirmed because the specimen involved was badly damaged. There is also an unconfirmed report from Cornell University in the USA (October 1998). 

In addition to the information provided in the History of Introduction table, A. vulgaris has been confirmed from Ireland. Kerney (1999), in his atlas of non-marine Mollusca, shows A. lusitanicus (=vulgaris) as an Irish species. However, subsequent research indicates that Kerney’s records are probably in error. The species has since been unequivocally recorded in Ireland by Anderson (2010).


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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Austria  1972 Yes Fischer and Reischütz (1998) Accidental
Belgium  1974 Yes De Winter (1989) Accidental
Bulgaria   Yes Wiktor (1983) Accidental; in Stara Planina
Czech Republic  1993 Yes Dvorák and Horsák (2003) Accidental
Denmark  1991 Yes Proschwitz and Winge (1994) Accidental
Falkland Islands UK Proschwitz TVon (1988) Accidental. In Port Stanley
Faroe Islands Denmark  1996 Yes Weidema (2006) Accidental
Finland  1990 Yes Valovirta (1995) Accidental; Aland Islands
Germany Yes von Proschwitz (1997) Accidental
Iceland  2003 Yes Ingimarsdóttir and Ólafsson (2005) Accidental
Italy   Yes Cesari (1978) Accidental
Liechtenstein   Cesari (1978) Accidental
Netherlands  1988 Yes De Winter (1989) Accidental
Norway  1988 Yes Proschwitz and Winge (1994) Accidental
Poland   Yes Kozlowski and Kornobis (1995) Accidental
Slovakia  1992 Yes Cejka et al. (2006) Accidental
Spain   Yes Chevallier (1981) Accidental; Catalunya
Sweden  1975 Yes Proschwitz TVon (1997) Accidental; southern Sweden
Switzerland  1955 Yes Turner et al. (1998) Accidental
UK   Yes Kerney (1999) Accidental

Risk of Introduction

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It is likely that A. vulgaris will continue to spread northwards and especially eastwards in Europe, to the Baltic States and Russia (Proschwitz, 1997). It may be expected to turn up eventually in the Antipodes and in North America.  

A survey of introduced slugs in California, USA, in which ITS sequencing based on UK material of the species was used, found only Arion rufus (R McDonnell, UCLA, personal communication, 2008).  

Many authors refer to its propensity for transport with plant materials through the horticultural trade and the gardening trade.


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A. vulgaris is most frequent in agricultural and horticultural habitats with permanent, dense vegetation, such as grassland, fallows and gardens, and is abundant in compost heaps. In low numbers, it is present in most agricultural and horticultural land, and also increasingly in natural habitats (Fechter and Falkner, 1990; Turner et al., 1998).

Habitat List

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Terrestrial – ManagedCultivated / agricultural land Principal habitat Harmful (pest or invasive)
Protected agriculture (e.g. glasshouse production) Secondary/tolerated habitat Harmful (pest or invasive)
Managed forests, plantations and orchards Secondary/tolerated habitat Harmful (pest or invasive)
Disturbed areas Principal habitat Harmful (pest or invasive)
Rail / roadsides Principal habitat Harmful (pest or invasive)
Urban / peri-urban areas Principal habitat Harmful (pest or invasive)
Terrestrial ‑ Natural / Semi-naturalNatural forests Secondary/tolerated habitat Harmful (pest or invasive)
Scrub / shrublands Secondary/tolerated habitat Harmful (pest or invasive)

Hosts/Species Affected

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A. vulgaris is a serious pest of diverse vegetable crops (especially Brassicaceae, lettuce, cucurbits), vegetable seedlings, arable crops (Triticaceae), ornamental plants, low-growing fruits (strawberries) and herbs within gardens in Central Europe, regularly causing severe losses. In the early stages of arable crop development (after seedling emergence or after planting), the plants are seriously defoliated or completely destroyed. The leaves, flowers or fruit may be damaged with feeding holes, and the potential harvest devalued. In Austria, serious damage to arable agriculture has been reported (Reischütz, 1984). In Poland, A. vulgaris was found to feed on a wide range of plants, including arable crops and commonly occurring weeds. Slug damage was found on 103 plant species (including wild species) and preferred crops including Brassica napus (Kozlowski and Kaluski, 2004; Kozlowski, 2005).


Host Plants and Other Plants Affected

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Plant nameFamilyContext
Asparagus officinalis (asparagus)LiliaceaeMain
Beta vulgaris (beetroot)ChenopodiaceaeOther
Brassica napus var. napus (rape)BrassicaceaeMain
Capsicum annuum (bell pepper)SolanaceaeOther
Cucurbita (pumpkin)CucurbitaceaeMain
Daucus carota (carrot)ApiaceaeMain
Foeniculum vulgare (fennel)ApiaceaeOther
Fragaria vesca (wild strawberry)RosaceaeMain
Lactuca sativa (lettuce)AsteraceaeMain
Phaseolus (beans)FabaceaeOther
Raphanus sativus (radish)BrassicaceaeOther
Solanum tuberosum (potato)SolanaceaeMain

Growth Stages

Top of page Flowering stage, Fruiting stage, Post-harvest, Pre-emergence, Seedling stage, Vegetative growing stage


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Copious deposits of slime and slime trails leading from damaged site indicate activity. 

Damage only within 1-5 m from the field edge, next to an area with dense, undisturbed vegetation, for example, grassland, fallow, scrub and garden.

Surface damage to large plants or plant parts specifically indicates the presence of this species. Complete removal of plants may occur.  

No damage occurs below ground with this species.


List of Symptoms/Signs

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SignLife StagesType
Fruit / external feeding
Fruit / frass visible
Fruit / reduced size
Inflorescence / external feeding
Leaves / external feeding
Leaves / frass visible
Leaves / shredding
Roots / external feeding
Seeds / external feeding
Stems / external feeding
Stems / visible frass
Vegetative organs / external feeding
Whole plant / external feeding
Whole plant / frass visible

Biology and Ecology

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A. vulgaris shows comparatively little genetic variation through its central European range (Quinteiro et al., 2005). Material from Britain, France and Italy gives no genetic indication of hybridisation with Arion ater or A. rufus. However, data on metabolic rates of individuals of these species from Sweden (Hagnell et al., 2003) appear to suggest hybridisation between A. vulgaris and A. rufus

Interpretation of these data is complicated by the suggestion (Chevallier, 1981; SM Davies, [address available from CABI], personal communication, 2008) that the A. ater complex in Europe comprises species additional to those presently recognized, i.e. A. ater, A. rufus and A. vulgaris

Reproductive Biology

A. vulgaris has an annual life cycle (Davies, 1987). In the British Isles, mating takes place between late July and early September. Courtship starts after sunset and copulation may take between 2 and 3 hours (Davies, 1987). The eggs are laid between September and November and the adults then die off. The juveniles appear in spring (March/April) and grow rapidly to maturity in June/July. 

It has been suggested that two generations can occur in especially favourable (warm, moist) environments.  

Physiology and Phenology

Due to the recent expansions in the range and the difficulty in distinguishing A. vulgaris from related species, few observations on regional phenotypic variability are reported. 

Chevallier (1977) noted a tendency for dark-coloured individuals to occur at higher altitudes in the species native range in France, and for brighter, reddish coloured individuals to predominate in warmer regions and at lower altitudes.  


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Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Ds - Continental climate with dry summer Tolerated Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)
ET - Tundra climate Tolerated Tundra climate (Average temp. of warmest month < 10°C and > 0°C)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Anas platyrhynchos Predator Adults/Juveniles not specific
Carabus Predator Eggs/Juveniles not specific
Cychrus caraboides Predator Eggs/Juveniles not specific
Erinaceus europaeus Predator Adults not specific
Phasmarhabditis hermaphrodita Parasite Adults not specific
Pterostichus Predator Eggs/Juveniles not specific
Silpha atrata Predator Adults/Juveniles not specific

Notes on Natural Enemies

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No natural enemies have yet been shown to substantially reduce the populations of A. vulgaris

Means of Movement and Dispersal

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Very little is known about the rates of spread of this species. The first dates of when it was recorded in various countries are given in the Distribution table. 

An introduction to new areas is always accidental and appears to occur with the movement of plant materials including garden and horticultural waste.

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Plants or parts of plants Yes Yes

Impact Summary

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Economic/livelihood Negative
Environment (generally) Negative

Economic Impact

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No overall assessment of the economic consequences of A. vulgaris has been made, but the species contributes to damage on several horticultural crops (Fischer and Reisschütz, 1998). Strawberry growers in Norway have reported more than 50% loss in yield due to A. vulgaris, but proper economic assessments have not been conducted yet (Weidema, 2006).

Environmental Impact

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Impact on Habitats

A. vulgaris can be a significant cause of defoliation of wild plants and even trees (Proschwitz, 1997). However, these effects are likely to be short-lived and the severity of defoliation will be dependent upon a number of environmental variables controlling slug breeding success. 

Impact on Biodiversity

The main impact on biodiversity noted by authors has been the decline in numbers and disappearance of Arion rufus in areas where A. vulgaris is abundant and invasive (Fischer and Reischütz, 1998).

Social Impact

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The use of toxic baits could have health impacts on children in gardens and on predators that may accumulate poisons. The volume of sales of garden slug killers in central Europe has been linked to the prevalence of this species (Weidema, 2006).

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Is a habitat generalist
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Pioneering in disturbed areas
  • Tolerant of shade
  • Capable of securing and ingesting a wide range of food
  • Benefits from human association (i.e. it is a human commensal)
  • Fast growing
  • Has high reproductive potential
  • Reproduces asexually
Impact outcomes
  • Changed gene pool/ selective loss of genotypes
  • Negatively impacts agriculture
  • Negatively impacts livelihoods
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Hybridization
  • Interaction with other invasive species
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Difficult to identify/detect in the field
  • Difficult/costly to control

Uses List

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  • Laboratory use
  • Research model

Detection and Inspection

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The occurrence of A. vulgaris in transported plant materials may involve the adults, juveniles or eggs. 

The adults and juveniles are active after dark and may be detected in the evening or early morning, or by inspecting plant materials stored under cover. Like Deroceras reticulatum, all stages hide in leaf whorls, under debris, stones and wood and occasionally in the soil around root systems. 

The eggs are deposited on the soil, under dead leaves or other surface debris and are not buried in the soil. 

Traps containing molluscicides (metaldehyde, carbamate, iron pyrophosphate hydrate) may be used to collect material, but hand collecting is often just as efficient and avoids the risk of contaminating produce.

Similarities to Other Species/Conditions

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A. vulgaris belongs to a clade of large round-back slugs inhabiting central, western and southern Europe. These include Arion rufus, which has been dispersed with trade to western North America. A. vulgaris and A. rufus are closely related and able to hybridize (Hagnell et al., 2003). 

Unfortunately, it is very difficult to distinguish between these two species based on external morphology. Reliable methods of discrimination include: dissection of the proximal genitalia in mature individuals; the use of ITS1 sequencing data based on known reference material. The spermatophores exchanged during sexual intercourse are highly diagnostic, but they are unlikely to be available routinely. A summary of the internal and external characteristics of A. vulgaris are given by Davies (1987). Quick (1960) provides a useful summary for A. rufus.  

There are two colour phases: a dark phase and a light phase, which can occur mixed in populations. 

The dark phase (red-brown, black body colours) of A. vulgaris has a sub-dermal black pigment masked by an overlying reddish pigment. The red pigment responds to environmental conditions and varies from bright red-brown (warm, dry conditions) to dark-brown or black (cold conditions) (Chevallier, 1977). Colour can alter within a generation if specimens are transplanted from warm to cold areas e.g. an increase in altitude or movement further north (R Anderson, [address available from CABI], personal communication, 2008). The foot fringe colour matches the overall body colour in the dark phase. In the dark phase of A. rufus there is no indication of contrasting pigment layers in the dermis. In addition, the foot fringe is brighter, yellow or red to orange, usually contrasting markedly with (duller) body colours that may include grey or pure black. 

The pale phase of A. vulgaris (yellowish to pale-brown body colours) lacks the contrasting dark subdermal pigment and the skin layers are uniform in colour. The pale phase is difficult to distinguish from A. rufus although the latter still tends to have brighter red to orange, contrasting foot fringes, whereas in A. vulgaris the foot fringe and body colours match better.   

Populations of A. vulgaris reproduce more by sexual means than by selfing. This is in contrast to other large Arions such as A. rufus, which commonly self. Discovery of copulating individuals, particularly during daylight hours, would tend to indicate A. vulgaris rather than A. rufus or Arion ater

Resting individuals of A. rufus, when stimulated by stroking the back firmly, will often react by rolling the body from side to side while in the contracted position. This reaction is extremely rare or non-existent in A. vulgaris (see Davies, 1987).


Prevention and Control

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Early Warning Systems

No warning system is available for A. vulgaris. However, in habitats that have been undisturbed for at least 2 years, A. vulgaris often occurs in high numbers and is likely to cause damage.

Cultural Control

Ploughing and other methods of soil cultivation significantly reduce slug populations, and the removal of vegetation deprives A. vulgaris of shelters. In recent years the establishment of fallows has been encouraged in many European countries as part of government-subsidized set-aside programmes. Along with grassland, fallows and other undisturbed habitats are excellent habitats for A. vulgaris. In these habitats, A. vulgaris builds up large populations and migrates into adjacent crops, often completely destroying the nearest few metres of the field. Thus, crops sensitive to slug feeding should not be sown or planted next to undisturbed habitats and undisturbed habitats should not be created next to a slug sensitive crop.

Biological Control

The nematode Phasmarhabditis hermaphrodita (Rhabditidae) is an effective biocontrol agent for many slug species (Wilson et al., 1993; Glen et al., 1996). Juvenile A. vulgaris are highly susceptible to P. hermaphrodita, but larger specimens are not susceptible (B Speiser, FiBL, Frick, Switzerland, unpublished data).

Chinese ducks are successfully used to control slugs in horticultural crops (B Grimm, Institute of Zoology, Graz, Austria, personal communication; B Speiser, FiBL, Frick, Switzerland) but their use is limited by the labour requirement of herd management. If ducks swallow A. vulgaris, they need access to water to clean their beaks (Sulzberger, 1996). The successful use of ducks for control of snails is described by Sakovich (1996).

Chemical Control

For chemical control of A. vulgaris, bait pellets are normally used. These contain either metaldehyde or a carbamate as active ingredient. The pellets are broadcast on the soil. If A. vulgaris migrates into the crop from an adjacent habitat, it may be sufficient to treat a narrow strip (0.5 m) with twice the dosage recommended for broadcast application (Friedli and Frank, 1998).

Host Resistance

There is little scope to reduce damage by A. vulgaris through the use of resistant varieties.

Gaps in Knowledge/Research Needs

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Quantification of economic impacts is missing from almost all evaluations and should be followed up. 

The status of A. vulgaris in the USA is unclear. Apart from an uncorroborated report on the internet (October 1998) for Cornell University, USA, no evidence for its occurrence there has been adduced. Despite this, almost the whole of continental USA falls within the latitudinal and climatic parameters suitable for this species. The relevant authorities are aware of the potential problem, but more studies addressing the identity of introduced large arionids in the USA are required. It has been established by a molecular study in California, USA (R McDonnell, UCLA, personal communication, 2008) that the invasive, large arionids in that area at least, are attributable to Arion rufus


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Links to Websites

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Conchological Society of Great Britain & Ireland
DAISIE (European Alien Species Expert Registry)


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Europe: DAISIE - Delivering Alien Invasive Species Inventories for Europe, Web-based service,

UK: Malacological Society of London, Canterbury Christ Church University , Kent, CT1 1QU,


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07/04/2008 Updated by:

Roy Anderson, Consultant, UK

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