New Zealand flatworm
Arthurdendyus triangulatus
Overview
Photo credit: ©The Food and Environment Research Agency (Fera)
Arthurdendyus triangulatus
Habitat:
Widely Spread Species:
Origin and Distribution:
Impacts:
How did it get here?
Is it found in Ireland or Northern Ireland?
You can help by reporting any sightings:
Prevent Spread:
Current Legislative Position (Listed on 14 August 2019)
Arthurdendyus triangulatus
Habitat:
- 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.
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.
- 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.
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.
You can help by reporting any sightings:
- If it is in Northern Ireland @ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.
- If your sighting is in Ireland please report @ the National Biodiversity Data Centre (NBDC).

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 resources:
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.