Deroceras reticulatum
Adult Deroceras reticulatum
Conservation status
Least Concern  (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Order:	Stylommatophora
Family:	Agriolimacidae
Genus:	Deroceras
Species:	D. reticulatum
Binomial name
Deroceras reticulatum (O. F. Müller, 1774)[1]
Synonyms[2]
Agriolimax reticulatus (Müller, 1774) Limax reticulatus Müller, 1774

Deroceras reticulatum, common names the "grey field slug", "grey garden slug", and "milky slug", is a species of small air-breathing land slug, a terrestrial pulmonate gastropod mollusc in the family Agriolimacidae. This species is an important agricultural pest.

Deroceras reticulatum is native to Europe, North Africa and the Atlantic Islands.^[2][3] It occurs widely in Europe, but is more rare and restricted to cultivated fields in the southeast, particularly in the Balkans, and is probably absent from Greece and the Bulgarian mountains.^[2] In the north and central European lowlands, Great Britain, and Ireland, it is probably the most widely occurring slug.^[2] In northern Scandinavia it is scarce, and is mainly found as a synanthrope.^[2]

This species occurs in countries and islands including:

• Great Britain
• Ireland
• Austria
• Spain
• Bulgaria
• Czech Republic^[4] – least concern (LC)^[5]
• Netherlands^[6]
• Poland
• Slovakia^[4]
• Sweden
• Latvia
• Ukraine^[7]

The species has been widely introduced as a synanthrope to many regions:

• North America,^[2] in parts of Northern Michigan and Southern Michigan
• Canada^{[citation needed]}
• Colombia^[8]
• Peru^[2]
• Argentina – major slug pest in Buenos Aires province^[9]
• Saint Helena^[10]
• Tasmania^[2]
• New Zealand^[2]
• central Asia^[2]

As all other Deroceras it has a short keel at the back of the body. Deroceras reticulatum is very variable in colour, creamy or light coffee cream, rarely blackish spotted (slugs with spots may appear blackish).^[2] Behind the mantle there is the dark spots form a reticulate pattern.^[2] The skin is thick.^[2] Mucus is colourless, on irritation milky white.^[2] The slug cannot be distinguished from many other Deroceras species based only on its external appearance.^[2]

This slug can be up to 40–60 mm long (preserved 25–30 mm).^[2] The size varies according to the habitat.^[2]

Reproductive system: Penis is fleshy and with a silky sheen, in the shape of an irregular sac, in fully mature specimens divided into 2 parts by a deep lateral constriction.^[2] Penial gland has very variable shape, usually a few branches or a single long branch.^[2] Stimulator is large, conical and narrow.^[2] Retractor of the penis is inserted laterally.^[2] Vas deferens opens into penis wall facing the external body side.^[2] Rectal caecum is large.^[2]

This slug can travel up to 40 feet (12.2 m) in one night.^[11]

Deroceras reticulatum is almost exclusively restricted to cultivated areas, usually in open habitats, in meadows, near roadsides, in ruins, gardens and parks, not inside forests.^[2] External appearance is very similar to Deroceras rodnae, Deroceras praecox and the internal anatomy is very similar to Deroceras turcicum, but those three species lives in natural habitats – in woods – and they co-occur with Deroceras reticulatum very rarely.^[3] It shelters under stones and ground litter (It does not burrow into the soil).^[2] It is active at night.^[2]

This species is omnivorous, feeding mainly on fresh leaves and fruits or seedings.^[2] Deroceras reticulatum is a serious pest of agricultural crops, garden cultivations^[2] and horticulture.^[11] After several years with continuous moist weather conditions abundance can seriously increase.^[2]

Life cycle covers a few months, usually two generations.^[2] The main reproductive phase is in summer and autumn.^[2] It lays hundreds of eggs which hatch during early summer.^[11]

Maximum age is about a year.^[2] Slugs die at the first frosts.^[2] Usually only eggs hibernate, sometimes also juveniles.^[2]

Various carabid beetles are predators of Deroceras reticlatum, including:

• the European garden beetle Carabus nemoralis, is a beneficial predator (from the human perspective) because it eats the young of this species and also their eggs.^[11]
• Pterostichus melanarius^[12]
• Pterostichus madidus^[9]
• Nebria brevicollis^[9]
• Scarites anthracinus eats eggs and slugs in Argentina.^[9]
• Poecilus cupreus^[12]

The bacterium Moraxella osloensis is a mutualistic symbiont of the slug-parasitic nematode Phasmarhabditis hermaphrodita.^[13] In nature, Phasmarhabditis hermaphrodita vectors Moraxella osloensis into the shell cavity of the slug host Deroceras reticulatum in which the bacteria multiply and kill the slug.^[13]

Deroceras reticulatum can transfer Escherichia coli on its body surface.^[14]

Parasites of Deroceras reticulatum include:

• Parelaphostrongylus tenuis^[15]

This article incorporates CC-BY-2.0 text from the reference ^[13] and public domain text from the reference.^[2]

• Spencer, H.G., Marshall, B.A. & Willan, R.C. (2009). Checklist of New Zealand living Mollusca. pp 196–219 in Gordon, D.P. (ed.) New Zealand inventory of biodiversity. Volume one. Kingdom Animalia: Radiata, Lophotrochozoa, Deuterostomia. Canterbury University Press, Christchurch

Media related to Deroceras reticulatum at Wikimedia Commons

• Deroceras reticulatum images at Encyclopedia of Life
• Fauna Europaea Search Distribution
• Deroceras reticulatum Archived 19 August 2009 at the Wayback Machine on the UF / IFAS Featured Creatures Web site