Chestnut Slug - Deroceras invadens

    Alt Name
    Deroceras panormitanum
    Description

    Usually pale blotchy brown, but can be darker. It can be distinguished from the commoner D. reticulatus by its finer, smoother tubercles and the dark sole. It also has a pale ring around the breathing pore, though this can be faint in some specimens. A useful ID tip is that it is a (relatively!) fast mover and is usually the first slug to slide away when disturbed.

    Similar Species

    Deroceras reticulatum is larger, has larger tubercles and a net-like pattern in the grooves. It has a pale sole. (see ID Aids below)

    Deroceras laeve is small (similar in size to D. invadens) and has a brown sole, concolorous with the body.

    Identification difficulty
    ID guidance
    • 20-25mm
    • short keel at rear of body
    • pale rim around the breathing pore
    Identification aids

    Netted Slug vs Chestnut Slug

    The Netted Slug, Derocerus reticulatum, is probably the most common and widespread slug in the UK. It can be found in almost all terrestrial habitats so is a species you are likely to encounter frequently. Whilst it is fairly straightforward to identify, it is most likely to be confused with the Chestnut Slug, Derocerus invadens, which is also common, particularly around buildings and in disturbed sites. So how can you be sure which is which?

    Firstly check that it is a Derocerus:

    • Small-medium size (15-30mm)
    • Pale coloured – a shade of off-white/pale grey/pale brown
    • No stripes or spots (the Netted Slug may have a few vague brown blotches)
    • A keel at the tip of the tail but only running a short way over the body
    • A whitish sole and colourless/milky mucus
    • Mantle (front section) is roughly half the length of the slug

    ID aid

    Habitat

    Found to be particularly common in Nurseries, but also found in parks and gardens.

    When to see it

    All year round.

    Life History

    Introduced to Britain in the early 1930s. It can lay around 30 eggs a week these take 2 weeks to hatch and reach sexual maturity in around eight weeks.

    UK Status

    Common over most of Britain and increasing.

    VC55 Status

    Common in Leicestershire and Rutland.

    Leicestershire & Rutland Map

    MAP KEY:

    Yellow squares = NBN records (all known data)
    Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

    UK Map