Slug

  • Scientific name: Arion hortensis (garden slug) / Limax maximus (great grey slug) / Arion ater (large black slug)
  • Type: Invertebrates

Key information

Several species are widespread and common in gardens:

  • Garden slug - Arion hortensis - up to 30 mm long, bluish-black with orange underside
  • Great grey slug - Limax maximus - up to 200 mm long, pale grey with dark spots
  • Large black slug - Arion ater - up to 150 mm long, jet black or orange with a black head. 

Slugs are similar to snails, but they have no shell. Instead they have a horny plate concealed under the mantle or saddle. Slugs are active only when the temperature is above 5 degrees C. In dry, cold weather they stay deep in the soil.

Slugs have both male and female reproductive cells (hermaphrodite), but must find a mate to exchange sperm before they can reproduce. They lay batches of gelatinous, watery eggs in moist crevices. The climatic conditions determine how quickly the eggs develop and hatch – the warmer it is, the quicker they develop. It takes about a year for slugs to mature into adults, which can live for about two years.

Slugs can be serious garden pests, eating seedlings, plants and fruit and vegetable crops. However they are eaten by a range of wildlife including hedgehogs, foxes, badgers, many birds, slow worms, violet ground beetles and Devil’s coach horses.

What they eat:

Slugs eat plant leaves, stems and roots, decaying matter and plant debris, fungi and earthworms.

Identifying features:

Natural habitats: Bog garden Compost heap Flower border Hedge Herb garden Lawn/grassy area Log pile Meadow area Patio Rock/stone pile Shrub Woodland area

Where and when to see them

You can find slugs throughout the garden, especially at night. Sometimes on the lawn after heavy rain. Also in hedgerows, meadows, parks and woods.

They can generally be seen at night in spring, summer and autumn.

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