The New Zealand Flatworm

Arthurdendyus triangulatus

Don O'Driscoll

I've had New Zealand Flatworms in my garden in Kinlochbervie for several years now.  I find them under stones especially in damp weather.  In this state they are coiled up usually with some mucous on them.  Coiled, they are up to 1 inch in diameter.  I suspect they're active at night and more so in damp weather.  If placed in a saucer of water, they are able to elongate themselves as seen in the photographs.  They are mainly a pale liver colour. The edges of the mantle are a grainy off-pink colour, and the underside is the same colour as the mantle.

In view of the potential damage these creatures can do (they feed on earthworms), anyone finding them in their garden should be very wary of transferring plants or soil out of the area. Advice on control is available from the HDRA website.  Worms may be found in gardens under boards or plastic sheeting, and can be killed in hot water or in concentrated salt solution, and then destroyed.

A map of their range is available on the NBN Gateway.  They are widespread in Highland, from east to west, and as far as the north coast.

Records of New Zealand Flatworms are very welcome. Report initially by email giving date, place, six-figure grid reference and any other relevant details. Specimens may be sent in cases of uncertainty (details on emailing).

Photos © Don O'Driscoll