Slug

Classification of the slugs

The ancestors of the slugs lived the seas. They evolved/moved and changed during time, to give some 103 today; 000 different, marine or terrestrial species. The most important evolution was the transformation of the Branchie S into Poumon S and an adaptation to the terrestrial environment by the production of a very particular Mucus. The slug remains however very dependant on moisture. They have an important ecological function while intervening in the control of the vegetation and the recycling of the Nécromasse. They offer a source of important food for many species of which birds. They cause problem for the farmers and the gardeners, problems which justified the production of specialized Pesticide S (anti-slugs or Limacide S), which alas proved Polluant S and poisons for much of other species. The alternative methods without poisons being not very compatible with the intensive agriculture, the slugs, like the Escargot S and of many Invertébré S much moved back or disappeared from most of their habitat, victim of the pesticides.

One counts it in Europe forty different species.

Place des slugs in the animal kingdom

Principal slugs met in France

Family/ Principal species

Arionidés

Large red slug: Arion rufus
Slug of the gardens: Arion hortensis
black Slug: Arion lusitanicus

Limacidés

Large gray slug: Limax maximus
Small gray slug: Deroceras reticulanum
Large yellow slug: Limax flavus

Milacidés

Milax gagates
Milax nigritans

Boettgerillidés

Boettgerilla pallens

Description of the slugs

The slugs measure between 1 and 15 cm. Their body is lengthened and can be divided ainsi :

Peak médiodorsale
Shield or coat
Tentacles
caudal mucous Gland
Plate of snaking

The head is provided with four Tentacule S located at the top of the Bouche; the tentacles superiors carry, at their end, the Yeux but constitute also tactile and olfactive bodies. The mouth comprises two Mâchoire S with small Dent S and a Langue, the Radula, it also toothed.

The shield or coat behind the head which recovers some grains or a small plate of limestone that one calls the limacelle one. One observes, on the line of the shield, the respiratory opening of the animal which one calls also Pneumostome.

The caudal part is the part located behind of the shield.

The foot is the ventral and muscular part animal. It adheres on the ground thanks to the plate of snaking.

Mucus

The Mucus of the slugs is a colloidal secretion complexes with high viscosity produced by specialized glands. Providing a lubricant function, it is essential to their progression. It effectively protects the slugs from the deshydradation and the infra-red radiation. But especially thanks to its antibiotic properties, it protects them from the viral, bacterial and fungic infections to which these animals would be without this protection very exposed.
Lorsque slug is subjected to aggression mechanical or chemical it produces immediately surplus of mucus, which makes it particularly viscous, which could perhaps sometimes enable him to escape the predatory awkward ones, in spite of its slowness. It is possible that mucus serf also to detoxicate the animal which can thus evacuate some Polluant S introduced with the plants.

During displacement, a gland located at the end before foot secretes this mucus which is crushed under the plate of snaking and allows them to slip. A part remains on the ground in the form of a very fine film with the iridescent reflections which can constitute an olfactive track making it possible to the individuals to find itself to reproduce.

Properties colloidal of mucus of slug could to play role in good progress of process of humification of litter and perhaps also for digestion of birds or animals which eats it voluntarily or involuntarily (like the cows, sheep or goat's milk cheeses considered herbivorous, but which introduce many invertebrates with their food), but these questions were not the subject of thorough studies.

It seems that the mucus of slug could have medicinal uses in the past (against the lung diseases or of the stomach). In spite of its common properties not very, it does not seem either to have been the object of pharmacological or ethnopharmacologic studies thorough.

Biology of the slugs

The slug is an animal with cold blood, primarily night or which is active only in very wet weather. Its activity varies much according to the periods of the year, the temperature and moisture.

The life cycle of the slugs, just like their population density, the speed of their reproduction and their growth are conditioned by the climatic conditions, the light and food available. The soft winters support the rate of survival of eggs, the young slugs and their development. The dry and cold winters can induce a reduction in the populations living on a piece.

Activity and lifestyle

The activity of the slug varies much according to the species and within the species according to the individuals, and for the same individual, one day to another.

The slugs leave during the night in general and activate themselves only in one fork of thermo-hygrometrical conditions (minimum/maximum)

The horticultural slugs are immobilized in lower part of 5°C. The optimum of temperatures of the gray slugs is at the neighborhoods of 18°C. They are inactive with 0°C. The slugs die in -3°C, but they in general hid in-depth before the arrival of freezing.

Without water or moisture, the slug cannot produce mucus and consequently cannot move. It takes refuge in the ground to await the return of the rains.

Food

The slugs have a varied food, generally made up of vegetable fabrics but they can also consume mushrooms and livestock wastes.

The large slug and the small gray slug rather consume the plants on the surface of the ground and seem attracted by already damaged plants. In period of dryness, the small slugs live rather in the ground and then nibble the underground parts of the plants or mushrooms pushing on plants in decomposition.

A slug can not eat during several days and introduce until the equivalent of half of its weight in only one night. The gray slug absorbs between 30 and 50 Mg per day, but the large slug can ingurgiter between 5 and 10 G per day. Certain slugs are nourished in only once, others feed on several occasions during the same night.

Reproduction

Like snail, the slug is hermaphrodite, i.e. the same individual is sometimes male and sometimes female. The male bodies are initially activated, then it is with the turn of the bodies females. The release of these two phases of the sexual activity is controlled by a hormonal system.

The female lays the egg S between a few days and several weeks after the coupling according to the species. A slug can lay between 100 and 500 eggs out of packages from 10 to 50. It deposits them in a hole dug in the ground or under a shelter. The eggs are spherical, yellow blanchâtres or transparencies.

The duration of incubation of eggs depends on the ic conditions Climat, in particular of the temperatures. With 5°C, incubation will last up to three months whereas for 20°C, two to three weeks suffice. The moisture of the ground must be ranging between 40% and 80%.

The slugs can give rise to a generation per annum, every two years or two per annum. The periods most favorable for the reproduction are the autumn and spring.

With the blossoming of eggs, the snails measure a few millimetres and are transparent. The slugs live of new in eighteen months according to the species and the area. The gray slug, for example, evolves/moves in a generation per annum in the areas at rigorous winter, in two generations per annum in the areas at soft winter.

On the other hand, the black slug develops in only one generation per annum whatever the area.

Displacements

The slugs move little. They can traverse in optimal conditions between 4 and 7 m daily for the gray slug, 2 and 3 m for the black slug. When they are located in a piece where the vegetation is abundant, the slugs do not disperse of more than 50 cm per day.

They locate their food thanks to their olfactive bodies and with taste buds.

Factors of development of the slugs

Factors/ Favorable indications

Moisture

Hygroscopy of the air
Moisture of the ground: in the first 5 centimetres of surface

Température
the quantity of introduced food depends on the temperature: maximum between 15 and 20°C

Standard of ground

Generally: aired grounds, wheatear and stony
Especially: clay soils and argilo-limestones,
Sometimes: muddy grounds,
Seldom: sandy grounds
Presence of Organic matter, remains vegetable, crop waste products
Proximity of slope, wood, meadows and fallow

Tillage

Reduction in the farming way
too surface Sowings

the precedents

Colza, cereals with straw, meadows and Fallow
Remains after harvest
Establishment of intermediate culture

Other factors

Irrigation
Direct drilling
Presence of Straw

Fight against the slugs

The products used to eliminate the slugs are called " Limacide s".

Method " pot of miel"

One can get rid of the slugs while placing a plant which they appreciate particularly (Consoude, Tagette) which will make that they will forsake the plants that you wish to protect.

Method of the trap

One buries containers on the level of the ground in which one pours Bière. The odor of beer attracts them and they drown there.

One can also pose a plank of wood so that they can take refuge there the night. In the morning, it is enough to turn over it and the birds and other animals (like the Orvet S, etc) will délecteront themselves of this delicious mets.

A liquid manure or a simple mulching of Fougère eagle also makes it possible to eliminate them in a natural way.

Method of the plants barriers

One surrounds the plants to be protected (salads, cauliflowers,…) plants barrier (Garlic, Onion S, Mustard, Parsley, Clover, Chervil, Potato, Nasturtium, Begonia S, Blackcurrant,…) definitely less appreciated slugs.

Natural enemies of the slugs

The slugs have the many predatory ones:

of many insects of which the Carabe S (in particular: anchomenis dorsalis (eggs), carabus auratus, platysma vulgare, poecilus cupreus, ophonus rufipes, morphocarbus monilis, abax ater), decimated by the Pesticide S and the pulling up of the Hedge S, the snail of Burgundy (which eats eggs), the glow-worm and its larvae, the chilopodes (chilopoda), Ischyropsalididae (it is faucheux, eats especially snails), ocypus olens
the majority of the Oiseau X,
the Brown bear and the Grizzly are famous to appreciate the large slugs
Mammifère S such as the Taupe S, the Hedgehog S, the Shrew S, the Rat S and the Badger X,
the Clamping plate S, the Frog S, the Slow worm S and the Lizard S, but they never eliminate totality from the slugs.

By leaving places not-maintained in the garden, one supports the development of predatory natural slugs (except perhaps the grizzly…). Especially the predatory insects have needs for refuges (stones, heap of sheets).

Photographs

Random links:

James Hutton | Izards | Rougier of Camarès | Rene Vernadet | Pierre Andreu