About 25mm long. The male has a swollen tip to his abdomen, but the female has a pointed tip which she uses to push her eggs into the soil. The larvae are the infamous root eating "leatherjackets", much disliked by gardeners everywhere. They also come to the surface at night and chew the base of stems. Large numbers may live under the lawn.
Information Source: http://www.uknature.co.uk/T.paludosa-info.html