View source for Slug

{{short description|Shell-less terrestrial gastropod mollusc}}
{{About|| marine slugs|Sea slug|snails|Snail|other uses|Slug (disambiguation)}}
{{pp-move}}
{{Use dmy dates|date=August 2018}}
{{paraphyletic group
| image = Slugs 1896.png
| image_caption = Various species of [[Great Britain|British]] land slugs, including (from the top) the larger drawings: ''[[Arion ater]]'', [[Kerry slug]], ''[[Limax maximus]]'' and ''[[Limax flavus]]''
| image2 = Slug in VanDusen Botanical Garden.jpg
| image2_caption=''[[Arion (genus)|Arion]]'' sp., from [[Vancouver]], [[British Columbia|BC]]
| auto = yes
| parent = Gastropoda
| includes = 
*[[Onchidiacea]]
*[[Soleolifera]]
* Multiple lineages within [[Sigmurethra]]<ref name=Burton1982>{{citation |journal=Tuatara |volume=25 |issue=2 |pages=48–63 |url=https://nzetc.victoria.ac.nz/tm/scholarly/tei-Bio25Tuat02-t1-body-d2.html |title=How to be sluggish}}</ref>
| excludes = 
}}
[[File:Slugonawall-zushi-2021-6-6.webm|thumb|A slug on a wall in [[Kanagawa Prefecture|Kanagawa]], [[Japan]].]]

'''Slug''', or '''land slug''', is a [[common name]] for any apparently shell-less [[Terrestrial mollusc|terrestrial]] [[gastropod]] [[mollusc]]. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a small internal shell, particularly [[sea slug]]s and [[semi-slug]]s (this is in contrast to the common name ''[[snail]]'', which applies to gastropods that have a coiled shell large enough that they can fully retract their soft parts into it).

Various [[Taxonomy (biology)|taxonomic]] families of land slugs form part of several quite different evolutionary lineages, which also include snails. Thus, the various families of slugs are not closely related, despite the superficial similarity in overall body form. The shell-less condition has arisen many times independently as an example of [[convergent evolution]], and thus the category "slug" is [[Polyphyly|polyphyletic]].

==Taxonomy==
Of the six orders of [[Pulmonata]], two – the [[Onchidiacea]] and [[Soleolifera]] – solely comprise slugs. A third group, the [[Sigmurethra]], contains various clades of snails, semi-slugs (i.e. snails whose shells are too small for them to retract fully into), and slugs.<ref name=Burton1982 /> The taxonomy of this group is in the process of being revised in light of DNA sequencing.<ref name=White2011>{{cite journal |last1=White |first1=T. R. |last2=Conrad |first2=M. M. |last3=Tseng |first3=R. |last4=Balayan |first4=S. |last5=Golding |first5=R. |last6=de Frias Martins |first6=A. M. |last7=Dayrat |first7=B. A. |year=2011 |title=Ten new complete mitochondrial genomes of pulmonates (Mollusca: Gastropoda) and their impact on phylogenetic relationships |journal=BMC Evolutionary Biology |volume=11 |issue=1 |page=295 |doi=10.1186/1471-2148-11-295 |pmid=21985526 |pmc=3198971 |doi-access=free |bibcode=2011BMCEE..11..295W }}</ref> Research suggests that pulmonates are paraphyletic and basal to the [[opisthobranch]]s, which are a terminal branch of the tree.<ref>{{Cite journal |last=Kocot |first=Kevin |date=December 2013 |title=Phylogenomics supports Panpulmonata: Opisthobranch paraphyly and key evolutionary steps in a major radiation of gastropod molluscs |url=https://www.sciencedirect.com/science/article/abs/pii/S1055790313002765 |journal=Molecular Phylogenetics and Evolution |volume=69 |issue=2 |pages=764-771 |via=Science Direct}}</ref> The family [[Ellobiidae]] are also polyphyletic.

*Subinfraorder [[Orthurethra]]
**Superfamily [[Achatinelloidea]] <small>Gulick, 1873</small>
**Superfamily [[Cochlicopoidea]] <small>Pilsbry, 1900</small>
**Superfamily [[Partuloidea]] <small>Pilsbry, 1900</small>
**Superfamily [[Pupilloidea]] <small>Turton, 1831</small>
*Subinfraorder [[Sigmurethra]]
**Superfamily [[Acavoidea]] <small>Pilsbry, 1895</small>
**Superfamily [[Achatinoidea]] <small>Swainson, 1840</small>
**Superfamily [[Aillyoidea]] <small>Baker, 1960</small>
**Superfamily [[Arionoidea]] <small>[[John Edward Gray|J.E. Gray]] in Turnton, 1840</small>
**Superfamily [[Athoracophoroidea]]
***Family [[Athoracophoridae]]
**Superfamily [[Orthalicoidea]]
***Subfamily [[Bulimulinae]]
**Superfamily [[Camaenoidea]] <small>Pilsbry, 1895</small>
**Superfamily [[Clausilioidea]] <small>[[Otto Andreas Lowson Mörch|Mörch]], 1864</small>
**Superfamily [[Dyakioidea]] <small>Gude & Woodward, 1921</small>
**Superfamily [[Gastrodontoidea]] <small>Tryon, 1866</small>
**Superfamily [[Helicoidea]] <small>[[Constantine Samuel Rafinesque|Rafinesque]], 1815</small>
**Superfamily [[Helixarionoidea]] <small>Bourguignat, 1877</small>
**Superfamily [[Limacoidea]] <small>[[Constantine Samuel Rafinesque|Rafinesque]], 1815</small>
**Superfamily [[Oleacinoidea]] <small>H. & A. Adams, 1855</small>
**Superfamily [[Orthalicoidea]] <small>Albers-Martens, 1860</small>
**Superfamily [[Plectopylidoidea]] <small>Moellendorf, 1900</small>
**Superfamily [[Polygyroidea]] <small>Pilsbry, 1894</small>
**Superfamily [[Punctoidea]] <small>Morse, 1864</small>
**Superfamily [[Rhytidoidea]] <small>Pilsbry, 1893</small>
***Family [[Rhytididae]]
**Superfamily [[Sagdidoidera]] <small>Pilsbry, 1895</small>
**Superfamily [[Staffordioidea]] <small>[[Johannes Thiele (zoologist)|Thiele]], 1931</small>
**Superfamily [[Streptaxoidea]] <small>[[John Edward Gray|J.E. Gray]], 1806</small>
**Superfamily [[Strophocheiloidea]] <small>[[Johannes Thiele (zoologist)|Thiele]], 1926</small>
**Superfamily [[Parmacelloidea]]
**Superfamily [[Zonitoidea]] <small>[[Otto Andreas Lowson Mörch|Mörch]], 1864</small>
**Superfamily [[Quijotoidea]] <small>Jesús Ortea and Juan José Bacallado, 2016</small>
***Family [[Quijotidae]]

==Description==
[[File:Slug parts.png|thumb|300px|The external anatomy of a slug|alt=Drawing of slug with labels for the foot (bottom side), the foot fringe that surrounds it, the mantle behind the head, the pneumostome for breathing, and the optical and sensory tentacles]]

The external anatomy of a slug includes the following:

* '''Tentacles''': Like other pulmonate land gastropods, the majority of land slugs have two pairs of 'feelers' or ''tentacles'' on their head. The upper pair is light-sensing and has eyespots at the ends, while the lower pair provides the [[olfaction|sense of smell]]. Both pairs are retractable in [[stylommatophora]]n slugs, but contractile in [[Veronicellidae|veronicellid]] slugs.
* '''Mantle{{anchor|Mantle}}''': On top of the slug, behind the head, is the saddle-shaped ''[[mantle (mollusc)|mantle]]''. In stylommatophoran slugs, on the right-hand side of the mantle is a [[respiratory]] opening, the [[pneumostome]], which is easier to see when open; also on the right side at the front are the genital opening and anus. Veronicellid slugs have a mantle covering the whole dorsal part of the body, they have no respiratory opening, and the anus opens posteriorly.
* '''Tail''': The part of a slug behind the mantle is called the 'tail'.
* '''Keel{{anchor|Keel}}''': Some species of slugs, for example ''[[Tandonia budapestensis]]'', have a prominent ridge running over their back along the middle of the tail (sometimes along the whole tail, sometimes only the posterior part).
* '''Foot''': The bottom side of a slug, which is flat, is called the 'foot'. Like almost all gastropods, a slug moves by rhythmic waves of [[muscular contraction]] on the underside of its foot. It simultaneously secretes a layer of [[mucus]] that it travels on, which helps prevent damage to the foot tissues.<ref name="biologists1">{{cite journal |last=Denny |first=M. W. |author2=Gosline, J. M. |title=The physical properties of the pedal mucus of the terrestrial slug, ''Ariolimax columbianus'' |journal=Journal of Experimental Biology |year=1980 |volume=88 |pages=375–393 |url=http://jeb.biologists.org/content/88/1/375.full.pdf |issue=1 |doi=10.1242/jeb.88.1.375}}</ref> Around the edge of the foot in some slugs is a structure called the 'foot fringe'.
* '''Vestigial shell''': Most slugs retain a remnant of their shell, which is usually internalized. This organ generally serves as storage for calcium salts, often in conjunction with the digestive glands.<ref name="Loest1979">{{Cite journal |jstor=30155937 |pages=461–469 |title=Ammonia Volatilization and Absorption by Terrestrial Gastropods_ a Comparison between Shelled and Shell-Less Species |journal=Physiological Zoology |volume=52 |issue=4 |year=1979 |last1=Loest |first1=R. A. |doi=10.1086/physzool.52.4.30155937 |s2cid=87142440 }}</ref> An internal shell is present in the [[Limacidae]]<ref name="Branson1980">{{cite journal | title = The recent Gastropoda of Oklahoma, Part VIII. The slug families Limacidae, Arionidae, Veronicellidae, and Philomycidae | author1 = Branson, B. A | journal = Proceedings of the Oklahoma Academy of Science
 | volume = 60 | pages = 29–35 | year = 1980}}</ref> and Parmacellidae.<ref>{{cite journal
 | title = Estudio de ''Parmacella valenciannesii'' Webb & Van Beneden, 1836, y consideraciones sobre la posicion sistematica de la familia Parmacellidae (Mollusca, Pulmonata, Stylommatophora)|journal=Boletín de la Sociedad de Historia Natural de les Baleares|year=1981|volume=25|pages=103–124| author1 = Alonso, M. R. | author2 = Ibañe, M. | url = http://www.raco.cat/index.php/BolletiSHNBalears/article/viewFile/171102/244828}}</ref> Adult [[Philomycidae]],<ref name="Branson1980" /> [[Onchidiidae]]<ref>{{cite journal
 | title = Review of the current knowledge of the systematics of Onchidiidae (Mollusca: Gastropoda: Pulmonata) with a checklist of nominal species | author1 = Dayrat, B. | journal = Zootaxa | volume = 2068 | pages = 1–26 | year = 2009| doi = 10.11646/zootaxa.2068.1.1 | s2cid = 4821033 }}</ref> and [[Veronicellidae]]<ref>{{cite journal | title = Valiguna flava (Heynemann, 1885) from Indonesia and Malaysia: Redescription and Comparison with Valiguna siamensis (Martens, 1867)(Gastropoda: Soleolifera: Veronicellidae) | author1 = Schilthuizen, M.
 | author2 = Thome, J. W. | journal = Veliger | volume = 50 | issue = 3 | pages = 163–170 | year = 2008}}</ref> lack shells.

==Physiology==
[[File:Ambigolimax.jpg|thumb|right|An active ''[[Ambigolimax]]'' slug in [[Fremont, California]]]]
Slugs' bodies are made up mostly of water and, without a full-sized shell, their soft tissues are prone to [[desiccation]]. They must generate protective mucus to survive. Many species are most active following rainfall or during nighttime since there is increased moisture on the ground. In drier conditions, they hide in damp places such as under [[tree bark]], fallen [[Trunk (botany)|logs]], rocks and manmade structures, such as [[Flowerpot|planters]], to help retain body moisture.<ref name="biologists1"/> Like all other gastropods, they undergo [[torsion (gastropod)|torsion]] (a 180° twisting of the internal organs) during development. Internally, slug anatomy clearly shows the effects of this rotation—but externally, the bodies of slugs appear more or less symmetrical, except the [[pneumostome]], which is on one side of the animal, normally the right-hand side.

Slugs produce two types of [[mucus]]: one is thin and watery, and the other thick and sticky. Both kinds are [[hygroscopy|hygroscopic]]. The thin mucus spreads from the foot's centre to its edges, whereas the thick mucus spreads from front to back. Slugs also produce thick mucus that coats the whole body of the animal.<ref name="biologists1"/> The mucus secreted by the foot contains fibres that help prevent the slug from slipping down vertical surfaces.

The "[[snail slime|slime]] trail" a slug leaves behind has some secondary effects: other slugs coming across a slime trail can recognise the slime trail as produced by one of the same species, which is useful in finding a mate. Following a slime trail is also part of the hunting behaviour of some carnivorous slugs.<ref name="biologists1"/> Body mucus provides some protection against predators, as it can make the slug hard to pick up and hold by a bird's beak, for example, or the mucus itself can be distasteful.<ref name=illinois1>{{cite web|last=Nixon|first=P|title=Slugs|url=http://hyg.ipm.illinois.edu/pastpest/199809g.html|website=Home, Yard & Garden Pest Newsletter|publisher=College of Agricultural, Consumer and Environmental Sciences, University of Illinois|access-date=14 December 2012}}</ref> Some slugs can also produce very sticky mucus which can incapacitate predators and can trap them within the secretion.<ref name=":0" /> Some species of slug, such as ''[[Limax maximus]]'', secrete slime cords to suspend a pair during copulation.

==Reproduction==
[[File:Slug eggs and baby.jpg|thumb|''[[Deroceras]]'' juvenile with eggs of another (larger) slug species, most likely Arionidae]]
[[File:Slugs Mating.jpg|thumb|left|Pair of mating slugs, suspended by [[mucous]] thread and pad on wall]]
[[File:Mating slugs.png|thumb|left|A pair of mating slugs]]
Slugs are [[hermaphrodite]]s, having both female and male reproductive organs.<ref name="theoystersgarter1">{{cite web |url=http://theoystersgarter.com/2008/03/24/perverted-cannibalistic-hermaphrodites-haunt-the-pacific-northwest/ |title=Perverted cannibalistic hermaphrodites haunt the Pacific Northwest! " The Oyster's Garter |publisher=Theoystersgarter.com |date=24 March 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080413003808/http://theoystersgarter.com/2008/03/24/perverted-cannibalistic-hermaphrodites-haunt-the-pacific-northwest/ |archive-date=13 April 2008 |access-date=15 August 2016}}</ref> Once a slug has located a mate, they encircle each other and sperm is exchanged through their protruded genitalia. 

[[Apophallation]] has been reported only in some species of banana slug (''[[Ariolimax]]'') and one species of ''[[Deroceras]]''. In the banana slugs, the penis sometimes becomes trapped inside the body of the partner. Apophallation allows the slugs to separate themselves by one or both of the slugs chewing off the other's or its own penis. Once the penis has been discarded, banana slugs are still able to mate using only the female parts of the reproductive system.<ref name="theoystersgarter1"/><ref>{{cite journal |author1=Reise, H |author2=Hutchinson, J.M.C. |title=Penis-biting slugs: wild claims and confusions |journal=Trends in Ecology and Evolution |date=2002 |volume=17 |issue=4 |page=163 |doi=10.1016/S0169-5347(02)02453-9 |url=http://www.senckenberg.de/files/content/forschung/abteilung/zoologie/malakologie/malak/hutch/hutchpub/tree3.pdf |access-date=15 August 2016}}</ref><ref>{{cite journal |author1=Leonard, J.L. |author2=Pearse, J.S. |author3=Harper, A.B. |title=Comparative reproductive biology of ''Ariolimax californicus'' and ''A. dolichophallus'' (Gastropoda; Stylommiatophora) |journal=Invertebrate Reproduction & Development |date=2002 |volume=41 |issue=1–3 |pages=83–93 |doi=10.1080/07924259.2002.9652738 |bibcode=2002InvRD..41...83L |s2cid=83829239 }}</ref>

In a temperate climate, slugs usually live one year outdoors. In greenhouses, many adult slugs may live for more than one year.<ref>{{Cite web |date=2005-04-04 |title=Slugs and Their Management, HYG-2010-95 |url=http://ohioline.osu.edu/hyg-fact/2000/2010.html |access-date=2023-07-12 |archive-date=4 April 2005 |archive-url=https://web.archive.org/web/20050404222301/http://ohioline.osu.edu/hyg-fact/2000/2010.html |url-status=bot: unknown }}</ref>

==Ecology==
Slugs play an important role in the [[ecosystem]] by eating decaying plant material and [[fungi]].<ref name="yukozimo1"/> Most carnivorous slugs on occasion also eat dead specimens of their own kind.

===Feeding habits===
[[File:Large Slug near Manali, India.jpg|thumb|left|250px|Large slug near [[Manali, India]]]]
Most species of slugs are generalists, feeding on a broad spectrum of organic materials, including leaves from living plants, [[lichen]]s, [[mushroom]]s, and even [[carrion]].<ref name="yukozimo1">{{cite web |url=http://animals.mom.me/slugs-eat-11378.html |title=What Do Slugs Eat? |publisher=animals.mom.me |access-date=15 August 2016}}</ref><ref name="Mycologia2002">{{cite journal |last1=Keller |first1=H. W. |author2=Snell, K. L. |year=2002 |title=Feeding activities of slugs on Myxomycetes and macrofungi |url=https://www.tandfonline.com/doi/full/10.1080/15572536.2003.11833169 |journal=Mycologia |volume=94 |issue=5 |pages=757–760 |doi=10.2307/3761690 |jstor=3761690 |pmid=21156549 |access-date=15 August 2016}}</ref> Some slugs are [[predator]]s and eat other slugs and [[snail]]s, or [[earthworm]]s.<ref name="yukozimo1"/><ref name=BBC>{{cite news |url=http://news.bbc.co.uk/2/hi/uk_news/wales/south_east/7498195.stm |title=Worm-eating slug found in garden ('''video''') |work=[[BBC News]] |date=10 July 2008 |access-date=15 August 2016}}</ref>

[[File:Slug feeding on fruit.jpg|thumb|right|''[[Lehmannia]]'' sp. feeding on a small fruit in [[Mexico City]]]]

Slugs can feed on a wide variety of [[vegetable]]s and [[herbs]],<ref>{{cite web |title=What Do Slugs Eat? |url=https://www.slugcuisine.co.uk/ |website=Slug Cuisine |access-date=25 July 2024}}</ref> including flowers such as [[petunia]]s, [[chrysanthemum]]s, [[asteraceae|daisies]], [[lobelia]], [[lilies]], [[dahlia]]s, [[narcissus (plant)|narcissus]], [[gentians]], [[Primulaceae|primroses]], [[begonia|tuberous begonias]], [[alcea|hollyhocks]], [[tagetes|marigolds]], and fruits such as [[strawberries]].<ref name=UMMZ /> They also feed on carrots, peas, apples, and cabbage that are offered as a sole food source.<ref name=Mycologia2002/>

Slugs from different families are [[fungivore]]s. It is the case in the [[Philomycidae]] (e. g. ''[[Philomycus carolinianus]]'' and ''[[Phylomicus flexuolaris]]'') and ''[[Ariolimacidae]]'' (''[[Banana slug|Ariolimax californianus]]''), which respectively feed on slime molds ([[Mycetozoa|myxomycetes]]) and mushrooms ([[basidiomycetes]]).<ref name=Mycologia2002/> Species of mushroom producing fungi used as food source by slugs include milk-caps (''[[Lactarius (fungus)|Lactarius]]'' spp.), the oyster mushroom (''[[Pleurotus ostreatus]]'') and the penny bun (''[[Boletus edulis]]''). Other genera such as ''[[Agaricus]]'', ''[[Pleurocybella]]'' and ''[[Russula]]'' are also eaten by slugs. Slime molds used as food source by slugs include ''[[Stemonitis axifera]]'' and ''[[Symphytocarpus flaccidus]]''.<ref name=Mycologia2002/> Some slugs are selective towards certain parts or developmental stages of the fungi they eat, though this is very variable. Depending on the species and other factors, slugs eat only fungi at specific stages of development. In other cases, whole mushrooms can be eaten, without any selection or bias towards [[ontogenetic]] stages.<ref name=Mycologia2002/>

===Predators===
Slugs are preyed upon by various [[vertebrate]]s and [[invertebrate]]s. The predation of slugs has been the subject of studies for at least a century. Because some species of slugs are considered [[agricultural pest]]s, research investments have been made to discover and investigate potential predators in order to establish biological control strategies.<ref name=South1992/>

====Vertebrates====
Slugs are preyed upon by virtually every major vertebrate group. With many examples among [[reptile]]s, [[bird]]s, [[mammal]]s, [[amphibian]]s and [[fish]], vertebrates can occasionally feed on, or be specialised predators of, slugs.<ref name=South1992/> Fish that feed on slugs include the brown trout (''[[Salmo trutta]]''), which occasionally feeds on ''[[Arion circumscriptus]]'', an ''[[Arionidae|arionid]]'' slug.<ref name=South1992>{{cite book |last=South |first=A. |title=Terrestrial Slugs: Biology, ecology and control |year=1992 |publisher=Chapman & Hall |location=Boundary Row, London, UK |isbn=978-0412368103 |pages=428 pp}}</ref> Similarly, the shortjaw kokopu (''[[Galaxias postvectis]]'') includes slugs in its diet.<ref name=McDowall>{{cite journal |last=McDowall |first=R. M. |author2=Main, M. R. |author3=West, D. W. |author4=Lyon, G. L. |title=Terrestrial and benthic foods in the diet of the shortjawed kokopu, ''Galaxias postvectis'' Clarke (Teleostei: Galaxiidae) |journal=New Zealand Journal of Marine and Freshwater Research |year=1996 |volume=30 |issue=2 |pages=257–269|doi=10.1080/00288330.1996.9516713 |doi-access=free|bibcode=1996NZJMF..30..257M }} {{free access}}</ref> Amphibians such as frogs and toads have long been regarded as important predators of slugs. Among them are species in the genus ''[[Bufo]]'', ''[[Rhinella]]'' and ''[[Ceratophrys]]''.<ref name=South1992/>

Reptiles that feed on slugs include mainly [[snake]]s and [[lizard]]s.<ref name=South1992/> Some [[Colubridae|colubrid]] snakes are known predators of slugs. Coastal populations of the garter snake, ''[[Thamnophis elegans]]'', have a specialised diet consisting of slugs, such as ''[[Ariolimax]]'', while inland populations have a generalized diet.<ref name=Britt2006>{{cite journal |last=Britt |first=E. J. |author2=Hicks, J. W. |author3=Bennett, A. F. |title=The energetic consequences of dietary specialization in populations of the garter snake, Thamnophis elegans |journal=Journal of Experimental Biology |year=2006 |volume=209 |pages=3164–3169 |doi=10.1242/jeb.02366 |url=http://jeb.biologists.org/content/209/16/3164.full |issue=16 |pmid=16888064 |doi-access=free}}</ref> One of its [[Congener (biology)|congeners]], the Northwestern garter snake (''[[Thamnophis ordinoides]]''), is not a specialized predator of slugs but occasionally feeds on them. The redbelly snake (''[[Storeria occipitomaculata]]'') and the brown snake (''[[Storeria dekayi]]'') feed mainly but not solely on slugs, while some species in the genus ''[[Dipsas]]'' (e.g. ''[[Dipsas neuwiedi]]'') and the common slug eater snake (''[[Duberria lutrix]]''), are exclusively slug eaters.<ref name=South1992/><ref>{{cite journal |last=Maia |first=T |author2=Dorigo, T. A. |author3=Gomes, S. R. |author4=Santos, S. B. |author5=Rocha, C. F. D. |title=''Sibynomorphus neuwiedi'' (Ihering, 1911) (Serpentes; Dipsadidae) and ''Potamojanuarius lamellatus'' (Semper, 1885) (Gastropoda; Veronicellidae): a trophic relationship revealed |journal=Biotemas |year=2012 |volume=25 |issue=1 |pages=211–213 |doi=10.5007/2175-7925.2012v25n1p211 |issn=2175-7925 |doi-access=free }}</ref> Several lizards include slugs in their diet. This is the case in the slowworm (''[[Anguis fragilis]]''), the bobtail lizard (''[[Tiliqua rugosa]]''), the she-oak skink (''[[Cyclodomorphus casuarinae]]'') and the common lizard (''[[Viviparous lizard|Zootoca vivipara]]'').<ref name=South1992/><ref name=Avery1966>{{cite journal |last=Avery |first=R. A. |title=Food and feeding habits of the Common lizard (Lacerta vivipara) in the west of England |journal=Journal of Zoology |year=1966 |volume=149 |issue=2 |pages=115–121 |doi=10.1111/j.1469-7998.1966.tb03886.x}}</ref><ref>{{cite journal|last=Hewer|first=A. M.|title=Tazmanian lizards|journal=Tazmanian Naturalist|year=1948|volume=1|issue=3|pages=8–11|url=http://www.tasfieldnats.org.au/TasNaturalist/Articles/1948/TasNat_1948_Vol1_No3_pp8-11_Hewer_TasmanianLizards.pdf|archive-url=https://web.archive.org/web/20130425171558/http://tasfieldnats.org.au/TasNaturalist/Articles/1948/TasNat_1948_Vol1_No3_pp8-11_Hewer_TasmanianLizards.pdf|url-status=dead|archive-date=25 April 2013}}</ref>

Birds that prey upon slugs include [[common blackbird]]s (''[[Turdus merula]]''), [[starling]]s (''[[Sturnus vulgaris]]''), [[rook (bird)|rooks]] (''[[Corvus frugilegus]]''), [[jackdaw]]s (''[[Corvus monedula]]''), [[owl]]s, [[vulture]]s and [[duck]]s. Studies on slug predation also cite [[fieldfare]]s (feeding on ''[[Deroceras reticulatum]]''), [[redwing]]s (feeding on ''[[Limax]]'' and ''[[Arion (gastropod)|Arion]]''), [[Thrush (bird)|thrushes]] (on ''[[Limax]]'' and ''[[Arion ater]]''), [[red grouse]] (on ''[[Deroceras]]'' and ''[[Arion hortensis]]''), [[game bird]]s, [[wryneck]]s (on ''[[Limax flavus]]''), [[rock dove]]s and [[charadriiform]] birds as slug predators.<ref name=South1992 />

Mammals that eat slugs include [[fox]]es, [[badger]]s and [[hedgehog]]s.<ref>{{cite web |url=http://cardiff.ac.uk/biosi/staffinfo/wocs2.html |title=Slug Control |publisher=Cardiff.ac.uk |url-status=dead |archive-url=https://web.archive.org/web/20130402220342/http://www.cardiff.ac.uk/biosi/staffinfo/wocs2.html |archive-date=2 April 2013 |access-date=15 August 2016}}</ref><ref>{{cite web |url=http://budgeting.thenest.com/ecological-benefits-slugs-31334.html |title=Ecological Benefits of Slugs |publisher=thenest.com |access-date=15 August 2016}}</ref>

====Invertebrates====
Beetles in the family [[Carabidae]], such as ''[[Carabus violaceus]]'' and ''[[Pterostichus melanarius]]'', are known to feed on slugs.<ref name=Paill2000>{{cite book |last1=Brandmayr |first1=P. |display-authors=etal |title=Natural History and Applied Ecology of Carabid Beetles |year=2000 |publisher=PENSOFT Publishers |location=Sofia, Moscow |pages=221–227 |chapter-url=https://books.google.com/books?id=guGltcZwD4AC&q=slug+diet&pg=PA221 |last2=Paill |first2= W. |chapter=Slugs as prey for larvae and imagines of ''Carabus violaceus'' (Coleoptera: Carabidae) |access-date=15 August 2016|isbn=9789546421005 }}</ref><ref name=Syomndson2000>{{cite journal|last=Symondson|first=W. O. C.|author2=Glen, D. M. |author3=Erickson, M. L. |author4=Liddell, J. E. |author5= Langdon, C. J. |title=Do earthworms help to sustain the slug predator Pterostichus melanarius (Coleoptera: Carabidae) within crops? Investigations using monoclonal antibodies|journal=Molecular Ecology|year=2000|volume=9|issue=9|pages=1279–1292|doi=10.1046/j.1365-294x.2000.01006.x|pmid=10972768|bibcode=2000MolEc...9.1279S |s2cid=23921693}}</ref> Ants are a common predator of slugs; some ant species are deterred by the slug's mucus coating, while others such as [[driver ant]]s will roll the slug in dirt to absorb its mucus.

===Parasites and parasitoids===
Slugs are [[parasitism|parasitised]] by several organisms, including [[acari]]<ref name="baker70"/><ref name="barker78"/> and a wide variety of [[nematode]]s.<ref name="Teixeira">{{cite journal |pages=487–9 |doi=10.1590/S0074-02761993000300020 |title=On the diversity of mollusc intermediate hosts of ''Angiostrongylus costaricensis'' Morera & Cespedes, 1971 in southern Brazil |year=1993|last1=Teixeira |first1=C. G. |last2=Thiengo |first2=S. C. |last3=Thome |first3=J. W. |last4=Medeiros|first4=A. B.|last5=Camillo-Coura |first5=L. |last6=Agostini |first6=A. A. |journal=Memórias do Instituto Oswaldo Cruz |volume=88 |issue=3 |pmid=8107609|doi-access=free }}</ref><ref name=Sanjaya/> The slug mite, ''[[Riccardoella limacum]]'', is known to parasitise several dozen species of molluscs, including many slugs, such as ''[[Deroceras reticulatum]]'', ''[[Arianta arbustorum]]'', ''[[Arion ater]]'', ''[[Arion hortensis]]'', ''[[Limax maximus]]'', ''[[Tandonia budapestensis]]'', ''[[Milax gagates]]'', and ''[[Tandonia sowerbyi]]''.<ref name="baker70">{{cite journal | last = Baker | first = R. A. | title = The food of ''Riccardoella limacum'' (Schrank) – Acari-Trombidiformes and its relationship with pulmonate molluscs
 | journal = [[Journal of Natural History]] | volume = 4 | issue = 4 | pages = 521–530 | year= 1978 | doi = 10.1080/00222937000770481 }}</ref><ref name="barker78">{{cite journal|last=Barker |first=G. M. |author2=Ramsay, G. W. |title=The slug mite ''Riccardoella limacum'' (Acari: Ereynetidae) in New Zealand |journal=New Zealand Entomologist |volume=6 |issue=4 |pages=441–443 |year=1978 |url=http://www.petsnails.co.uk/docs/Volume_6-4-441-443.pdf |doi=10.1080/00779962.1978.9722316 |url-status=dead |archive-url=https://web.archive.org/web/20080705210933/http://www.petsnails.co.uk/docs/Volume_6-4-441-443.pdf |archive-date=5 July 2008 }}</ref> ''R. limacum'' can often be seen swarming about their host's body, and live in its respiratory cavity.

Several species of nematodes are known to parasitise slugs. The nematode worms ''[[Agfa flexilis]]'' and ''[[Angiostoma limacis]]'' respectively live in the [[salivary glands]] and [[rectum]] of ''[[Limax maximus]]''.<ref name="Taylor">[[John William Taylor|Taylor J. W.]] (1902). Part 8, pages 1–52. [https://archive.org/details/monographoflandf814tayl ''Monograph of the land and freshwater Mollusca of the British Isles. Testacellidae. Limacidae. Arionidae'']. Taylor Brothers, Leeds. Introduction [https://archive.org/stream/monographoflandf814tayl#page/n22/mode/1up page XV.], pages [https://archive.org/stream/monographoflandf814tayl#page/34/mode/1up 34]–52.</ref> Species of widely known medical importance pertaining to the genus ''[[Angiostrongylus]]'' are also parasites of slugs. Both ''[[Angiostrongylus costaricensis]]'' and ''[[Angiostrongylus cantonensis]]'', a [[meningitis]]-causing nematode, have larval stages that can only live in molluscs, including slugs, such as ''[[Limax maximus]]''.<ref name="Teixeira"/>

Insects such as [[dipterans]] are known [[parasitoid]]s of molluscs. To complete their development, many dipterans use slugs as hosts during their [[ontogeny]]. Some species of blow-flies ([[Calliphoridae]]) in the genus ''[[Melinda (fly)|Melinda]]'' are known parasitoids of [[Arionidae]], [[Limacidae]] and [[Philomycidae]]. Flies in the family [[Phoridae]], specially those in the genus ''[[Megaselia]]'', are parasitoids of [[Agriolimacidae]], including many species of ''[[Deroceras]]''.<ref name=Robinson1968>{{cite journal|last=Robinson|first=W. H.|author2=Foote, B. A.|title=Biology and Immature Stages of ''Megaselia aequalis'', a Phorid Predator of Slug Eggs|journal=Annals of the Entomological Society of America|year=1968|volume=61|issue=6|pages=1587–1594|doi=10.1093/aesa/61.6.1587}}</ref> House flies in the family [[Muscidae]], mainly those in the genus ''[[Sarcophaga]]'', are facultative parasitoids of Arionidae.<ref name=Barker2004CH3>{{cite book|title=Natural Enemies of Terrestrial Molluscs|year=2004|publisher=CABI Publishing|location=Wallingford, Oxfordshire, UK|isbn=978-0851993195|pages=88–124|chapter-url=https://books.google.com/books?id=bjAh_Gszsy8C&q=%22Notes+on+beetle+predators+of+molluscs%22&pg=PA37|author=Coupland, J. B.|editor=Barker, G. M|chapter=Chapter 3: Dipteras as predators and parasitoids of terrestrial gastropods, with emphasis on Phoridae, Calliphoridae, Sarcophagidae, Muscidae and Fannidae}}</ref>

==Behavior==
[[File:Muelheim an der Ruhr - Arion rufus - contraction.webm|right|thumb|A slug retracts its head and contracts its body after being touched]]
[[File:Geomalacus maculosus 3.jpg|right|thumb|alt=A brown and yellow spotted slug curled up into a tight ball so that its head is withdrawn completely, its mantle edge and tail are nearly touching, and none of its foot surface is exposed|The alarm response posture of the [[Kerry slug]], which is found only in this species]]
When attacked, slugs can contract their body, making themselves harder and more compact and more still and round. By doing this, they become firmly attached to the [[Substrate (biology)|substrate]]. This, combined with the slippery mucus they produce, makes slugs more difficult for predators to grasp. The unpleasant taste of the mucus is also a deterrent.<ref name="illinois1"/> Slugs can also incapacitate predators through the production of a highly sticky and elastic mucus which can trap predators in the secretion.<ref name=":0">{{Cite journal|last1=Gould|first1=John|last2=Valdez|first2=Jose W.|last3=Upton|first3=Rose|date=2019-02-08|title=Adhesive defence mucus secretions in the red triangle slug (Triboniophorus graeffei) can incapacitate adult frogs|url=https://onlinelibrary.wiley.com/doi/full/10.1111/eth.12875|journal=Ethology|volume=125|issue=8 |pages=587–591|doi=10.1111/eth.12875|bibcode=2019Ethol.125..587G |access-date=|s2cid=92677691}}</ref>

Some species present different response behaviors when attacked, such as the [[Kerry slug]]. In contrast to the general behavioral pattern, the Kerry slug retracts its head, lets go of the substrate, rolls up completely, and stays contracted in a ball-like shape.<ref name="background2008">
{{Cite journal|title=Forestry and Kerry Slug Guidelines |date=12 July 2009 |publisher=Forest Service Department of Agriculture, Fisheries and Food |url=https://www.agriculture.gov.ie/media/migration/forestry/forestservicegeneralinformation/kerryslugandotter/091207ForestryandKerrySlugGuidelines211209.pdf |url-status=dead |archive-url=https://web.archive.org/web/20130719063513/http://www.agriculture.gov.ie/media/migration/forestry/forestservicegeneralinformation/kerryslugandotter/091207ForestryandKerrySlugGuidelines211209.pdf |archive-date=19 July 2013 }} 9 pp.</ref> This is a unique feature among all the [[Arionidae]],<ref name="Kerney">{{cite book |title=Die Landschnecken Nord- und Mitteleuropas |author1=Kerney, M. P |author2=Cameron, A. D. |author3=Jungbluth, J. H.  |name-list-style=amp |year=1983|publisher=Verlag Paul Parey |location=Hamburg and Berlin |isbn=978-3-490-17918-0 |page=138|language=de}}</ref> and among most other slugs.<ref name="background2008"/> Some slugs can self-amputate ([[autotomy]]) a portion of their tail to help the slug escape from a predator.<ref>{{Cite journal |author=Pekarinen, E. |year=1994 |title=Autotomy in arionid and limacid slug |journal=Journal of Molluscan Studies |volume=60 |issue=1 |pages=19–23 |doi=10.1093/mollus/60.1.19|citeseerx=10.1.1.873.8562 }}</ref> Some slug species [[hibernate]] underground during the winter in temperate climates, but in other species, the adults die in the autumn.<ref name=UMMZ>{{cite web |last=Sandy |title=''Arion lusitanicus'' |url=http://animaldiversity.ummz.umich.edu/accounts/Arion_lusitanicus/ |website=Animal Diversity Web |publisher=University of Michigan Museum of Zoology |access-date=14 December 2012 |author2=Misner, L |author3=Balog}}</ref>

Intra- and inter-specific [[agonistic behavior]] is documented, but varies greatly among slug species. Slugs often resort to aggression, attacking both [[conspecific]]s and individuals from other species when competing for resources. This aggressiveness is also influenced by [[seasonality]], because the availability of resources such as shelter and food may be compromised due to [[climatic]] conditions. Slugs are prone to attack during the summer, when the availability of resources is reduced. During winter, the aggressive responses are substituted by a [[gregarious]] behavior.<ref name=Rollo1979>{{cite journal |last=Rollo |first=C. D. |author2=Wellington, W. G. |title=Intra- and inter-specific agonistic behavior among terrestrial slugs (Pulmonata: Stylommatophora) |journal=Canadian Journal of Zoology |year=1979 |volume=57 |issue=4 |pages=846–855 |doi=10.1139/z79-104 }}</ref>

==Human relevance==
The great majority of slug species are harmless to humans and to their interests, but a small number of species are serious pests of agriculture and horticulture. They can destroy foliage faster than plants can grow, thus killing even fairly large plants. They also feed on fruits and vegetables prior to harvest, making holes in the crop, which can make individual items unsuitable to sell for aesthetic reasons, and can make the crop more vulnerable to rot and disease.<ref>{{cite web|url=https://www.lovethegarden.com/uk-en/product/slugclear-ultra-3-685g|title=SlugClear Ultra: Highly efficient protection against slugs and snails &#124; Gardening tips and advice |publisher=LoveTheGarden.com |access-date=19 November 2012}}</ref>  Excessive buildup of slugs within some wastewater treatment plants with inadequate screening have been found to cause process issues resulting in increased energy and chemical use.<ref>Thompson, M. (2018) [https://digitalcommons.unl.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1016&context=envengdiss 'Evaluating Opportunities and Barriers to Improving the Energy Efficiency of Small Nebraska Wastewater Treatment Plants', pp.83] {{Webarchive|url=https://web.archive.org/web/20220606012829/https://digitalcommons.unl.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=1016&context=envengdiss |date=6 June 2022 }}</ref>

In a few rare cases, humans have developed ''[[Angiostrongylus cantonensis]]''-induced [[meningitis]] from eating raw slugs.<ref>{{cite web |url=https://www.abc.net.au/science/news/health/HealthRepublish_969551.htm |title=Health and Medicals News – Man's brain infected by eating slugs |website=[[Australian Broadcasting Corporation]] |access-date=15 March 2006}}</ref> Live slugs that are accidentally eaten with improperly cleaned vegetables (such as [[lettuce]]), or improperly cooked slugs (for use in recipes requiring larger slugs such as [[banana slug]]s), can act as a vector for a parasitic infection in humans.<ref name=Sanjaya>Senanayake, S. N.; Pryor, D. S.; Walker, J.; Konecny, P. (2003).[https://www.mja.com.au/journal/2003/179/8/first-report-human-angiostrongyliasis-acquired-sydney "First report of human angiostrongyliasis acquired in Sydney"] {{Webarchive|url=https://web.archive.org/web/20220730032313/https://www.mja.com.au/journal/2003/179/8/first-report-human-angiostrongyliasis-acquired-sydney |date=30 July 2022 }}. ''[[The Medical Journal of Australia]]'' '''179''' (8): 430–431.</ref><ref>{{cite web|author=Anna Salleh|url=http://www.abc.net.au/science/news/health/HealthRepublish_969551.htm|title=''Man's brain infected by eating slugs''|website=[[Australian Broadcasting Corporation]]|date=20 October 2003}}</ref>

===Prevention===
{{Main|Molluscicide}}
As control measures, baits are commonly used in both agriculture and the garden. In recent years, [[Iron(III) phosphate|iron phosphate]] baits have emerged and are preferred over the more toxic [[metaldehyde]], especially because domestic or wild animals may be exposed to the bait. The environmentally safer iron phosphate has been shown to be at least as effective as baits.<ref>{{cite web |url=https://extension.oregonstate.edu/news/less-toxic-iron-phosphate-slug-bait-proves-effective|title=Less toxic iron phosphate slug bait proves effective |publisher=Extension.oregonstate.edu |access-date=2 March 2014|date= 25 February 2008}}</ref> Methiocarb baits are no longer widely used. Parasitic nematodes (''[[Phasmarhabditis hermaphrodita]]'') are a commercially available biological control method that are effective against a wide range of common slug species. The nematodes are applied in water and actively seek out slugs in the soil and infect them, leading to the death of the slug. This control method is suitable for use in organic growing systems.

Other slug control methods are generally ineffective on a large scale, but can be somewhat useful in small gardens. These include {{ill|beer trap|de|Bierfalle|lt=beer traps}},<ref>{{cite web |url=http://www.gardening-guru.co.uk/2010/04/11/slugs-traps-death-by-beer/ |title=~ Slug Traps ~ Death by Beer Offers and Reviews |publisher=Gardening-guru.co.uk |access-date=16 November 2012 |archive-url=https://web.archive.org/web/20121118081908/http://www.gardening-guru.co.uk/2010/04/11/slugs-traps-death-by-beer/ |archive-date=18 November 2012 |url-status=dead |df=dmy-all }}</ref><ref>{{cite web|url=http://www.asthegardenturns.com/garden-pests/how-to-get-rid-of-slugs-and-snails/|title=How to Get Rid of Slugs and Snails|publisher=asthegardenturns.com|access-date=8 August 2016}}</ref> [[diatomaceous earth]],<ref>{{cite web |title=Using Diatomaceous Earth for Slugs |url=https://www.slugcuisine.co.uk/diatomaceous-earth/ |website=Slug Cuisine |access-date=25 July 2024}}</ref> crushed eggshells, [[coffee grounds]], and copper.<ref>{{cite web |title=Guide to Using Copper Slug Tape |url=https://www.slugcuisine.co.uk/copper-tape-guide/ |website=Slug Cuisine |access-date=25 July 2024}}</ref> Salt kills slugs by causing water to leave the body owing to [[osmosis]]<ref>{{cite web|url=http://www.newton.dep.anl.gov/askasci/gen06/gen06261.htm |title=Slugs and Osmosis |publisher=Newton.dep.anl.gov |access-date=2 March 2014}}</ref> but this is not used for agricultural control as [[soil salinity]] is detrimental to crops.{{citation needed|date=August 2018}} [[Conservation tillage]] worsens slug infestations. Hammond et al. 1999 find [[maize|maize/corn]] and [[soybean]] in the US to be more severely affected under low till because this increases organic matter, thus providing food and shelter.<ref name="Capinera-2020">{{cite book | last=Capinera | first=John | title=Handbook of vegetable pests | publisher=[[Academic Press]] | publication-place=[[London]], [[San Diego]], CA, USA | year=2020 | isbn=978-0-12-814488-6 | oclc=1152284558 | edition=2}} {{ISBN|9780128144893}}.</ref>

==Gallery==
<gallery mode="packed" heights="150">
File:Orange slug.jpg|''[[Red slug|Arion rufus]]''
File:Bug moving dead snail with fly 1a.jpg|A [[dung beetle]] (''[[Geotrupes stercorarius]]'') moving a dead slug.
File:Amanita amerimuscaria 126174.jpg|A [[mushroom]] (''[[Amanita muscaria]]'') being eaten by a [[banana slug]].
File:Slug damaging vegetables.jpg|Slugs eating [[vegetable]]s.
File:Jõelähtme Parish, Harju County, Estonia - panoramio - Николай Семёнов (4).jpg|''[[Limax cinereoniger]]'', the world's largest terrestrial slug.
File:GrallariaRufocinereaSmit (cropped).jpg|An illustration by [[Joseph Smit]] of a [[bicolored antpitta]] catching a slug.
</gallery>

==See also==

* [[Snail]]
* [[Sea slug]]

==References==
{{reflist|30em}}

==Further reading==
*{{cite journal|author= Burton, D. W. |date=January 1982 |title=How to be sluggish |journal=Tuatara |volume=25|issue=2 |pages=48–63|url=https://nzetc.victoria.ac.nz/tm/scholarly/tei-Bio25Tuat02-t1-body-d2.html}}

==External links==
*{{Commons-inline}}
* [https://web.archive.org/web/20050404222301/http://ohioline.osu.edu/hyg-fact/2000/2010.html Slugs and Their Management.] Ohio State University Extension. 	
*{{Cite web |url=http://www.nature.org/wherewework/northamerica/states/washington/misc/art30642.html |title=The Secret Lives of Jumping Slugs. |access-date=9 February 2010 |archive-url=https://web.archive.org/web/20100413130622/http://www.nature.org/wherewework/northamerica/states/washington/misc/art30642.html |archive-date=13 April 2010 |url-status=dead |df=dmy-all }} The Nature Conservancy.
* [https://digital.library.unt.edu/permalink/meta-dc-1506:1 Land Slugs and Snails and Their Control.] USDA Farmer's Bulletin No. 1895. Revised 1959. Hosted by the [https://web.archive.org/web/20071009202026/http://www.library.unt.edu/govinfo/digital-collections UNT Government Documents Department]
*[https://entnemdept.ufl.edu/creatures/misc/gastro/slugs_of_florida.htm Slugs of Florida]. [[University of Florida]] [[Institute of Food and Agricultural Sciences|IFAS]]

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[[Category:Stylommatophora|Stylommatophora]]
[[Category:Gastropod anatomy]]
[[Category:Articles containing video clips]]
[[Category:Mollusc common names]]
[[Category:Polyphyletic groups]]