They are usually found coiled up under stones, wood or pieces of polythene, not crawling about unless distrubed and heading for cover. When feeding they seem to lie on top of the earthworm, perhaps using their sticky mucus to hold on, excrete digestive enzymes and consume the soup that results. They either wait for the worms to surface or follow their borrows and other channels in the soil. So species of earthworm which stay near to the surface are more at risk. When the food supply decreases they shrink in size and can survive in this state for one or two years until the worms return.
Reproduction is asexual by parthogenesis, ie.
At first the content is a milky liquid, but this develops into two to eleven small flatworms in an oval egg about 7-8 mm accross. Their threat to soil condition and the wildlife which feed on earthworms cannot be overstated, and every means should be employed to prevent their spread and eradicate them if possible. Some pastures in Northern Ireland have become waterlogged due to the loss of the earthworm population. Unfortunately many have been shared between friends as they swap plants. There are no approved chemical controls, but Ground and Rove beetle adults and larve are known to prey on the adults.