Limax maximus, known also as “the giant garden slug,” is an invasive, terrestrial member of the phylum Mollusca, class gastropoda (Gaitán-Espitia 2012). Some other common names include “tiger slug” and “great grey slug” (McDonnell et. al. 2009). Recognizable by its black spots and yellowish-gray body coloration, this slug can reach lengths of 100 mm or greater (Simpson 1901). This gastropod’s native geographic distribution is in Europe, North Africa, and Asia Minor (Western Palearctic) (Gaitán-Espitia 2012). These slugs are constricted to living in places where they can have easy access to water since they have poor ability to retain water and easily dry out during the day (Kaya and Mitani 2000). Therefore, this need for moisture is partially why this mollusk is nocturnal (Boycott 1934). It has been introduced as a troublesome pest to North America, New Zealand, South America, Australia, and some Pacific Islands (Gaitán-Espitia 2012). The amount of dampness in an area determines the time able to be spent breeding and feeding since water is necessary to form mucus for movement and eating (Boycott 1934). Also known as the “greenhouse slug,” this invader is a generalist that has wreaked havoc on horticultural plants worldwide (Kaya and Mitani 2000). This gastropod eats fresh and rotting plants, more specifically tubers, fruits, leaves, roots, bulb flowers, ornamental plants, and perennial herbs (Kozlowski 2012). Though these slugs are simultaneous hermaphrodites, they are unable to self-fertilize (Simpson 1901). Instead, a unique, complex, lengthy mating procession occurs in which male parts of two of these gastropods intertwine (Pilsbry 1948). These slugs tend to not be seen in groups (McDonnell et. al. 2009).
Boycott, A. E. 1934. The Habitats of Land Mollusca in Britain. Journal of Ecology 22:1–38.
Gaitán-Espitia, J. D., M. Franco, J. L. Bartheld, and R. F. Nespolo. 2012. Repeatability of energy metabolism and resistance to dehydration in the invasive slug Limax maximus. Invertebrate Biology 131:11–18.
Kaya, H. K., and D. K. Mitani. 1999. Molluscicidal Nematodes for Biological Control of Pest Slugs. Pages 1–4. . Davis.
Kozłowski, J. 2012. The Significance of Alien and Invasive Slug Species for Plant Communities in Agrocenoses. Journal of Plant Protection Research 52:67–77.
Mc Donnell, R. J., T. D. Timothy D. Paine, and M. J. Gormally. 2009. Slugs: A Guide to the Invasive and Native Fauna of California. Pages 1–21. Oakland.
Pilsbry, H. A. 1948. Land Mollusca of North America: (north of Mexico). The Academy of Natural Sciences of Philadelphia 2:524–527.
Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) This species is fairly cosmopolitan globally but probably has a European origin in Europe, North Africa, and Asia Minor. It has been introduced widely around the world including Asia Minor, Australia, Canada, Europe, Mexico, New Zealand, the United States (including Hawaii and Alaska), Africa, and South America.
Native to: S and W Europe (mainly in disturbed areas to the north) (Rollo & Wellington 1979), Asia Minor, and Algeria (Thompson 2008).
Non-native in: South Africa, N America, Australia, New Zealand (Herbert 1997), Japan (Azuma 1982).
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Regularity: Regularly occurring
Type of Residency: Year-round
This slug is an introduced species in North America and other temperate regions of the world.
Biogeographic Regions: nearctic (Introduced )
Spotted garden slugs can attain at least 6 inches in length. They vary in color from yellowish-gray to brown with black spots on the mantle near the head and black stripes extending along the rest of the body. The tail area is wrinkled. There is a pneumostome or breathing pore on the back part of the mantle that this slug uses to breathe.
Range length: 15.24 (high) cm.
Other Physical Features: bilateral symmetry
Sexual Dimorphism: sexes alike
External: Light brown to gray body; multiple dark longitudinal stripes often breaking into spots on dorsum; mantle marbled; tentacles red-brown; whitish sole; clear mucus (Rollo & Wellington 1979).
Internal: Internal shell 11 x 7 mm; long, narrow, pale ovotestis; long, convoluted penis has an internal fold and a "comb" toward its apex; no rectal caecum (Quick 1960; Kerney & Cameron 1979).
Similar to L. cereoniger but no spotted tentacles or dark outer sections of sole (Rollo & Wellington 1979), smaller tubercles, shorter keel, larger jaw and internal shell, and penis smaller and narrows toward its base (Quick 1960; Sysoev & Schileyko, 2009).
Juveniles similar to Lehmannia marginatus and Ambigolimax valentianus except L. maximus has less mucus, no lyre banding on the mantle (Rollo & Wellington 1979), and bands on the sides (Quick 1960).
Eggs: 5.0 x 5.5 mm eggs, translucent and amber(Quick 1960).
Juveniles: light gray with side bands and light pink-gray tentacles at hatching; body bands and mantle coloration appears in 2-3 weeks (Quick 1960).
100-200 mm long extended (Rollo & Wellington 1979).
The Great Grey Slug (dark grey with whitish spots) can grow to 20 cm long, with a keel, or raised ridge, that runs about a third of the way along its back from the rear. It also has a 'fingerprint' pattern of raised ridges on the mantle. The pulmonary aperture opens on the right-hand side, near the back of the mantle.
Habitat Type: Terrestrial
Comments: This species is common in gardens and buildings, and margins of native forests, but does not seem to penetrate far into undistrubed forests, although it can be abundant in modified forest remnants and secondary forests (Barker, 1999).
Spotted garden slugs are found in moist places in fields, woods, and gardens. They inhabit damp ground under wood, rocks, vegetation, and other shaded areas.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest
Outsides of buildings, waste piles (Cook & Radford 1988), forests, hedgerows, gardens (Rollo & Wellington 1979).
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Comments: This nocturnal slug feeds primarily on decaying plant material and fungi, but because it shows aggresive behavior towards other slugs, it is often erroneously regarded as a predator (Barker, 1999).
Spotted garden slugs will eat fungi, decaying organic matter, and plants.
Plant Foods: leaves; lichens
Other Foods: fungus; detritus
Feeds on dead plants, fungus, domestic waste, carrion, and garden and crop plants (Herbert 2010). Prefers fungi and dead plants to live plants; eats oatmeal in captivity (Quick 1960).
This slug may help cycle nutrients in soil via its feeding activities.
They may be an intermediate host for trematodes and nematode worms.
Certain kinds of protozoans may be parasitic in them.
Ecosystem Impact: biodegradation
- ciliated protozoans
When irritated, spotted garden slugs will secrete a colorless mucus. A slug may lift its tail and vibrate it back and forth as a means of scaring a potential predator. It may clamp its mantle to the ground to protect its head. To scare away predators, it may even squirt blood through its breathing hole!
- Thamnophis sirtalis
- other Aves
- other small Mammalia
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: > 300
Comments: This species was first recorded in Hawaii either in 1931 or 1949 (Cowie, 1997) and has become established on Hawaii. In a recent survey, it was found in the Pua Akala region, southern part of Hakalua Forest National Wildlife Refuge, on the windward slopes of Mauna Kea, elevation 5150-6240 feet, Hawaii, Hawaiian Islands (Howarth et al., 2003). It had been documented historically in Colorado (Cockerell, 1927) but recent (2008) specimens exist in the University of Colorado Museum. In California, it occurs in 13 counties: Alameda, Calaveras, Humboldt, Kern, Los Angeles, Marin, Orange, Sacramento, San Bernardino, San Diego, San Francisco, Santa Barbara (incl. Santa Cruz Island), and Santa Clara (McDonnell et al., 2009). In New York, Hotopp and Pearce (2007) report it from 9 counties in the eastern, southeastern and far western parts of the state as an exotic. Forsyth (2005) documented it in the Upper Fraser Basin of central British Columbia in a single area in Quesnel but it is now widespread in southern British Columbia. Most recently, it was discovered in the Ktunaxa Traditional Territory in southeastern British Columbia (which extends from near Canada - U.S. border north to about 50 km north of Cranbrook) (Ovaska and Sopuck, 2009).
The mating ritual involves two slugs climbing onto something high, usually a twig, then lowering themselves on a rope of slime. They then intertwine, in mid-air, and extrude their genitalia to exchange sperm.
Life History and Behavior
L. maximus is an aggressive slug species both in the wild and the lab, especially in high densities, often killing and eating other slugs both of their own and other species (Rollo & Wellington 1979).
Defends itself through tail-wagging (and slapping) and quick fleeing (Rollo & Wellington 1979).
Homes to shelter (Cook 1979).
Engages in a conspicuous form of mating. A pair of L. maximus hangs from a long mucus thread, their bodies and blue-white penes encircle each other, and they exchange sperm on the ends of their penes (Quick 1960).
Eggs are approximately 1/4 inch in diameter, and when first laid, they are colorless and transparent. Gradually, the eggs become cloudy, resembling small pearls. Development is direct whereby larval stages occur within the egg, and eventually, tiny slugs emerge from the eggs. Limax becomes sexually mature in two years.
Lives 3-4 years. Eggs are laid in early spring and fall (Quick 1960).
This slug may live up to three years.
A pair of slugs will hang by a mucus string from a branch while they mate.
Egg size in late summer is smaller than egg size in autumn. In addition, clutch sizes are larger in summer than in autumn. In the autumn, a clutch size may be 50 to 130 eggs. Spotted garden slugs may exhibit aggression toward other slugs or snails when shelter sites for breeding are scarce.
Range number of offspring: 130.0 (high) .
Key Reproductive Features: simultaneous hermaphrodite; sequential hermaphrodite (Protandrous ); sexual ; fertilization (Internal ); oviparous
Parental Investment: no parental involvement
Molecular Biology and Genetics
Barcode data: Limax maximus
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Limax maximus
Public Records: 10
Specimens with Barcodes: 21
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNA - Not Applicable
Rounded National Status Rank: NNA - Not Applicable
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: This species is fairly cosmopolitan globally but probably has a European origin in Europe, North Africa, and Asia Minor. It has been introduced widely around the world including Asia Minor, Australia, Canada, Europe, Mexico, New Zealand, the United States (including Hawaii and Alaska), Africa, and South America.
Relevance to Humans and Ecosystems
Economic Importance for Humans: Negative
This slug has been known to damage gardens. It may be an intermediate host for some trematode and nematode worms which can harm our pets.
Negative Impacts: crop pest; causes or carries domestic animal disease
Economic Importance for Humans: Positive
This slug may contribute to regeneration of soil because of its eating habits.
Limax maximus (literally, "biggest slug"), known by the common names great grey slug and leopard slug, is a species of slug in the family Limacidae, the keeled slugs. It is among the largest keeled slugs, Limax cinereoniger being the largest.
Limax maximus is the type species of the genus Limax. The adult slug measures 10-20 cm (4-8 in) in length and is generally a light greyish or grey-brown with darker spots and blotches, although the coloration and exact patterning of the body of this slug species is quite variable.
This species has a very unusual and distinctive mating method, where the pair of slugs use a thick thread of mucus to hang suspended in the air from a tree branch or other structure.
Although native to Europe, this species has been accidentally introduced to many other parts of the world.
The greater part of the body is rounded, but there is a short keel on its tail, with about 48 longitudinal rows of elongate, detached tubercles. The body color is pale-grey, ash-colored, brownish or sometimes yellowish-white. The body is longitudinally streaked or spotted with black. The pattern of spotting is variable. The shield is always black-spotted. The sole of the foot is a uniform ash or yellowish-ash color. The foot-fringe is pale, with a row of minute submarginal blackish tubercles.
The shield is oblong, about one-third of the total length of the animal. The shield is rounded in front, angular behind, and forming an angle of about 80 degrees when in motion, usually of a similar tint to the body, but boldly marbled or maculate with black, somewhat concentrically and interruptedly ridged around a sub-posterior nucleus.
The pneumostome is just posterior to the midpoint of the mantle, as it is in all Limacidae.
Although color varieties have no actual taxonomic significance, a large number of color varieties have been described, prominent among them being the varieties serpentinus, vulgaris, cellarius (typical), johnstoni, maculatus, ferrussaci, obscurus, fasciatus and rufescens, of Alfred Moquin-Tandon, and cornaliee, of Pini.
The shell of Limax maximus is reduced and internal, under the shield. The occurrence of this internal shell was known to Pliny the Elder; the shell was used by the ancient physicians for the sake of its carbonate of lime.
The calcitic shell is situated beneath the hinder part of the shield, and is perceptible through the skin. The color of the shell is whitish. The shape of the shell is oblong-oval and thin, slightly convex above, and correspondingly concave beneath, with a membranous margin. The apex or nucleus is at the posterior margin but inclined towards the left side, and forming the apophysis by which the shell is organically attached to the animal. The length of the shell is 13 mm (1/2 inch) and the width of the shell is 7 mm (1/4 inch). Shells of different Limacidae species are undiagnostic: in other words, they are not helpful for identification purpose.
Digestive system: The formula of the radula is: 62-73/ × 138-157. The intestine has six convolutions and is without a caecum. Of the six convolutions of the intestine, four are imbedded in the liver, and two hang freely in the body cavity.
The nervous system is composed of the typical ganglia. The pedal ganglia are placed beneath the radula sac and joined together by an anterior and a posterior commissure. The abdominal ganglion lies a little to the right of the median line. The visceral ganglia occupy the angle between the lingual sheath and the oesophagus and the buccal ganglia are widely separated but joined together by a commissure nearly as thick as the ganglia themselves.
Reproductive system: The hermaphrodite gland (HG) is elongated and large, and is connected with spermoviduct (SD) by means of the hermaphrodite duct (HD) which takes its course through a portion of the albumen gland (AG). The spermoviduct is thick and well convoluted, and separates further down into a vas deferens or sperm-duct (VD) and an oviduct (OV). The former opens into the upper end of a very long penis (P), to which a strong retractor muscle (PRM) is attached. The lower portion of the penis unites with that of the oviduct at the genital orifice, so that there is no vestibule. The receptaculum seminis (RS) opens into the lower end of the penis near the junction of the two ducts.
The internal shells of the different species of Limacidae are not recognizable to the species level. Therefore, the fossil distribution of Limax maximus (and other Limacidae species) is unknown. Unidentified calcitic shells of Limacidae are known from European Tertiary and Quaternary deposits.
Within Europe, this species occurs in many areas, including:
- Great Britain - Limax maximus was first described England in Animalium Angliae Tres Tractatus … Alter de Cochleis tum Terrestribus tum Fluviatilibus by Martin Lister in 1678. The presence of Limax maximus in England had been noted twelve years earlier in Christopher Merret's Pinax Rerum Naturalium Britannicarum.
- Benelux: Belgium, Netherlands, Luxembourg
The non-indigenous distribution of Limax maximus includes:
- Central Europe: Czech Republic, Poland, Slovakia, Hungary, Germany, Austria
- Northern Europe - Scandinavia: Norway, Sweden (possibly the type locality), Faroe Islands
- Eastern Europe: Latvia, Lithuania, Belarus, Ukraine
Its introduction into the United States was first announced by George Washington Tryon in 1867, when it was discovered in cellars in Philadelphia. Within a few years its presence was noticed at Newport, Rhode Island, Brooklyn, and Pittsburgh, and it is now common in many areas, including:
- East Coast states
- Southern Ontario Canada
- South Central United States
- West Coast states, including California since 1896, and Montana
It can be found in some parts of Canada. In 2012 it was found in south-central Ontario, Nova Scotia, and western Newfoundland. In 2014 it was found in British Columbia in the South Okanagan area. Other non-indigenous distribution areas include Madeira, southern Africa, Australia, including Tasmania, New Zealand, Chile, and southern Brazil.
Limax maximus is nocturnal, feeding at night. It is not very active or prolific. When alarmed, or at rest, this slug merely draws its head within the shield, but does not otherwise contract its body. When irritated, it is said to expand its shield.
The homing faculty is strongly developed in this species, which, after its nocturnal rambles or foraging expeditions, usually returns to the particular crevice or chink in which it has established itself.
Limax maximus is capable of associative learning, specifically classical conditioning, because it is capable of aversion learning and other types of learning. It can also detect deficiencies in a nutritionally incomplete diet if the essential amino acid methionine is experimentally removed from its food.
The slug is almost always found near human habitation — usually in lawns, gardens, cellars or in other damp areas.
This species is not gregarious. It frequents gardens, damp and shady hedgerows and woods, hiding during the day beneath stones, under fallen trees, or other obscure and damp places. It does however exhibit a decided preference for the vicinity of human habitations, and readily takes up its abode in damp cellars or outbuildings.
In Ireland, this predilection for human dwellings is not exhibited, and the species is restricted to woods and other similar places. It may even be met almost within a high-water mark on the seashore.
Limax maximus is omnivorous. It is a detrivore, cleaning up dead plants and fungi, and a carnivore known to pursue other slugs at a top speed of 6 inches per minute. It also eats young crops faster than they can grow and so is listed as a major agricultural pest by state departments of agriculture in the US from Florida to Oregon.
The eggs of this slug are deposited in a cluster, slightly attached to each other. Eggs are transparent, elastic and slightly yellowish in color. The size of the egg is 6×4.5 mm. They hatch in about a month.
The tiny slugs which emerge from the eggs need at least two years to reach sexual maturity.
The lifespan of Limax maximus is 2.5–3 years.
The mating habits of Limax maximus are considered unusual among slugs: the hermaphrodite slugs court, usually for hours, by circling and licking each other. After this, the slugs will climb into a tree or other high area and then, entwined together, lower themselves on a thick string of mucus, evert their white translucent mating organs (penises) from their gonopores (openings on the right side of the head), entwine these organs, and exchange sperm. Both participants will later lay hundreds of eggs.
Parasites of Limax maximus include the nematode Agfa flexilis, which lives in its salivary glands,[unreliable source?] the nematode Angiostoma limacis, which lives in its rectum,[unreliable source?] and Angiostrongylus costaricensis.
A meningitis-causing nematode, Angiostrongylus cantonensis, which normally infests the lungs of rats, has a larval stage which can only live in molluscs, including slugs. This nematode was once known to be a problem only in tropical areas, but it has since spread to other regions. Live slugs that are accidentally eaten with improperly cleaned vegetables, such as lettuce, or slugs which have been improperly cooked, can act as vectors for the parasite.
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- (Latin) Linnaeus C. 1758. Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. pp. [1-4], 1-824. Holmiae. (Salvius).
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- Marshall, B. (2014). Limax maximus Linnaeus, 1758. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=819992 on 2014-11-06
- (German) M.P. Kerney, A. D. Cameron, J. H. Jungbluth: Die Landschnecken Nord- und Mitteleuropas. Verlag Paul Parey, Hamburg und Berlin 1983, ISBN 3-490-17918-8, page 183.
- Taylor, J. W. (7 November) 1902. part 8, pages 1-52. Monograph of the land and freshwater Mollusca of the British Isles. Testacellidae. Limacidae. Arionidae. Taylor Brothers, Leeds. Introduction page XV., pages 34-52.
- Tryon G. W. 1885. Manual of Conchology. Second series: Pulmonata Volume 1. Testacellidae, Oleacinidae, Streptaxidae, Helicoidea, Vitrinidae, Limacidae, Arionidae. 364 pp., 60 plates, pages 189-190, plate 46 figure 31-35, 39; plate 49, figure 76.
- Scharff R. F. (July) 1891. The slugs of Ireland. The Scientific Transactions of the Royal Dublin Society, volume IV., series II. Dublin, Royal Dublin Society; London, Williams & Norgate. 513-563. Limax maximus on pages page 517-521. plate LVII.
- Pini. 1876. Bull. Soc. Mal. Ital. ii., 83. (There is described Limax cornaliae Pini)
- Jeffreys J. G. 1862. British conchology: or, an account of the Mollusca which now inhabit the British Isles and the surrounding seas. Volume I. Land and freshwater shells. page 137-138.
- (Slovak) Lisický, M. J. (1991). Mollusca Slovenska [The Slovak molluscs]. VEDA vydavateľstvo Slovenskej akadémie vied, Bratislava, 344 pp.
- Kerney, M. P. & R.A.D. Cameron, 1979, A Field Guide to the Land Snails of Britain and North-west Europe. Collins, Glasgow.
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- LIMAX MACIMUS New slug found in the Faroes in 2003
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- Giant Garden Slug — Limax maximus. Montana Field Guide. Retrieved on 31 July 2009.
- Aguilera, P. A. 2001.Babosas de importancia económica en Chile.
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- Florida IFAS.
- UC Davis IPM.
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