New Zealand flatworm

Arthurdendyus triangulatus



  • Photo credit: ©The Food and Environment Research Agency (Fera)

  • Arthurdendyus triangulatus

  • Habitat: Undisturbed soils near the surface. Under cover such as rocks and stones.

  • Description: 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.

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

  • Impacts: 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 Ireland.

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

  • Is it found in Ireland or 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. The species is present in the Republic of Ireland but may be under recorded. More information can be found at NBDC and NBN Atlas NI.

Static Distribution Map as of December 2019 - Courtesy of CEDaR

Prevent Spread

• Inspect incoming consignments of plants

• Maintain good hygiene

• Inspect your site for flatworms

• Check plant products for flatworms

• Report sightings

Further guidance and ID downloads;

  • 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 Non Native Invasive Species Team in the Northern Ireland Environment Agency on 028 9056 9558.
Invasive Species Ireland

Invasive Species Ireland