Feed on grass roots from September and through to the following summer and are the legless greyish brown larvae of the crane fly (daddy long legs).
They pupate in the summer and adults emerge, sometimes in huge numbers in August, ready to lay eggs again. The larvae weaken the lawn which can then be pulled up by birds feeding on the larvae.
Larvae may move from lawn areas to neighbouring flower beds.
Control with Parasitic nematodes (Steinernema feltiae) . A microscopic transparent worm that feeds and multiplies within the larvae. Apply mid-September to a well-watered lawn. Best applied in the evening or on a dull day, soil temperature must be at least 10 degrees C.
Treatment can be repeated in the spring with severe infestations.