The larvae of crane flies, called leatherjackets, live in the soil and feed on roots and shoots (which they pull into the ground of mainly grasses and cereal crops. The adults do not cause any damage.
Life cycle and appearance of Crane flies
Adult crane flies are large flies with females reaching 45-50 mm across. They have long, spindly legs and one pair of narrow, clear wings with clearly visible veins. Eggs are black in colour, oval, 1mm long and deposited on the soil surface. Larvae are cylindrical, tapering toward the head, and grey-brown in colour. Larvae have 4 instars (larval stages) an reach 2.5 cm in length when fully grown. Pupae are greyish-brown, and 2.5 cm long. After adults emerge, part of the pupal case can be found sticking out above the soil surface.
Adult common crane flies emerge from the soil in late summer to fall, and females mate and lay 200-300 eggs. Larvae emerge within one week and then feed on roots and crowns of grasses during the autumn.. Larvae overwinter in the soil, usually in the third instar stage. and start feeding again in spring. They become active again and feed voraciously when the soil begins to warm up in spring. The larvae pupate below the soil surface in summer. The pupal stage lasts about two weeks.
Larval feeding causes brown spots in grasslands, turf and cereal fields. Exit holes of the burrows of the larvae might also be visible. Secondary damage may come from birds and rodents feeding on larvae and digging up turf.