When humans transport insects to different countries, the effects can be terrible on the species already living in that country. A New Zealand flatworm, called Artioposthia, caused havoc, when it arrived in the British Isles. It grows to up to 8 in (20 cm) long, and hunts for earthworms in the top 12 in (30 cm) of soil. It has greatly reduced earthworm numbers in places where it has spread. In Northern Ireland, some pastures have been totally cleared of earthworms by the invader.