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By Angela Stroud
Geographic Range
Arion ater is a terrestrial slug, common in England and the Pacific Northwest. (BBC 2000).
Biogeographic Regions:
nearctic 
(native ); palearctic (native ).
Habitat
Arion ater prefer grassy fields and crops of vegetation. Strictly terrestrial, they typically live in moist, cool soil (Long 1999).
Terrestrial Biomes:
savanna or grassland .
Physical Description
Although thought to be shell-less snails, Arion ater do have disc-type shells embedded in their mantle. This is surrounded by a fleshy oval tissue on their back. Slugs move about via a foot that, when flexed, allows the slug to control its movement.
Most Arion ater are orange when hatched, have a "straw" coloration until aproximately one inch in length, and eventually take on a black coloration. Typical slugs are about six inches long at maturity. (Branley 1996).
Reproduction
Although Arion ater are hermaphroditic, they do engage in cross-fertilization when a mate is available. After copulation, the slug may lay 20-50 eggs in crevices made in soil or in the cracks of decaying wood. These eggs typically hatch in six weeks (BBC 2000).
Key reproductive features:
simultaneous hermaphrodite; sexual ; fertilization (internal ); oviparous .
Behavior
While relatively dormant during the day, slugs rely on the coolness of the night to search for food. Soil surfaces must be moist for slugs to safely move around. In fact one practice of gardeners is watering their plants early in the morning so that the ground is not so moist at night, when slugs are active. This is particularly useful when combatting Arion ater--considered the most destructive species of slugs (Long 1999).
Food Habits
Arion ater spend most of their time eating. This is done with an enclosed radula that contains transverse rows of sharp teeth. The slug's diet consists mostly of fungi and plants, but is occasionally supplemented by worms, insects, decaying vegetation, and feces. Slugs feed mostly at night when conditions are cool and moist (Long 1999).
Economic Importance for Humans: Negative
Slugs are often a nuisance to horticulturists because of their choice of diet. Lettuce is a crop that is heavily damaged by slugs. Any sort of vegetation is at risk to slug damage. Arion ater is considered to be among the most destructive of the slugs (Long 1999).
Economic Importance for Humans: Positive
In general, slugs are crucial to a healthy ecosystem. They work to recycle decaying food and fecal matter that is then processed back through the soil. Without slugs working in such a manner, soil could potentially lose many of its nutrients (Nickel 1998).
Conservation Status
IUCN Red List: [link]:
Not Evaluated.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
State of Michigan List: [link]:
No special status.
This species is given no special conservation status.
Other Comments
Slugs have very few natural predators. The mucus that they secrete leaves the slugs sticky and slimy, and is thought that the mucus is highly distasteful. Among the slugs' natural predators are the hedgehog, badger, shrew, mole, mouse, frog, toad, snake, carnivorous beetle, and some birds (Nickel 1998).
Contributors
Angela Stroud (author), Southwestern University.
Stephanie Fabritius (editor), Southwestern University.
