New Zealand flatworm

Arthurdendyus triangulatus


Photo credit: ©The Food and Environment Research Agency (Fera)
Arthurdendyus triangulatus
  • Undisturbed soils near the surface. Under cover such as rocks and stones.

Widely Spread Species:
  • Under Article 19 of Invasive Alien Species Regulation (1143/2014) New Zealand flatworm has been identified as a Widely Spread Species in Northern Ireland and as such, management measures have been put in place to minimise its impacts.

  • Unlike the well known native earthworm, the invasive New Zealand flatworm does not have the segmented body that is easily recognised.
  • The flatworm does, as the name suggests, have a flattened body that is pointed at both ends and covered in sticky mucus.
  • Colour can vary making it difficult for members of the public to identify but in general specimens are grey, or brown, with a pale yellow margin and underside covered by specks.

Download N.I.E.A. ID guide

Origin and Distribution:
  • A. triangulatus originates from New Zealand however other species of predatory flatworms originate from Australia and elsewhere.

  • Earthworms form a pivotal function in terrestrial ecosystems in Ireland. They are responsible for aerating the soil and decomposing plant material while also regulating drainage to some extent by creating burrows.
  • The New Zealand flatworm has been shown to significantly reduce earthworm numbers from both agricultural lands and gardens in Northern Ireland and Ireland.

How did it get here?
  • It is believed that this species arrived in Northern Ireland and Ireland via the horticulture trade by contamination of plant potting soil from New Zealand.

Is it found in Northern Ireland?
  • The New Zealand Flatworm was introduced to Northern Ireland in the early 60’s. It is currently known from all 6 counties in Northern Ireland where it is generally concentrated around built up urban areas such as Belfast.
  • More distribution information can be found at  NBN Atlas NI.

You can help by reporting any sightings: @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.
Prevent Spread:
  • Inspect incoming consignments of plants
  • Maintain good hygiene
  • Inspect your site for flatworms
  • Check plant products for flatworms
  • Report sightings.

Further resources:


Video produced by BeBiodiversity

Current Legislative Position (Listed on 14 August 2019)
  • This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.
For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email:

Species Related Files:

Invasive Species Northern Ireland

Invasive Species Northern Ireland