Crane flies are medium to large insects that resemble large mosquitoes. In fact they are related to mosquitoes as both are "primitive flies"; delicate flies with long antennae. "Higher flies" like house flies tend to be heavier-bodied, stronger fliers with short, bristle-like antennae. Unlike mosquitoes, however, adult crane flies don't feed and are harmless. Crane fly larvae live in the soil and feed on plant roots.
Most crane fly species are confined to wet soils but a few have adapted to dryer soils which has allowed them to invade lawns and turf areas.
adult European crane fly
Crane fly life cycle
Crane fly eggs are laid in summer and larvae begin feeding on plant roots in fall. Larvae feed throughout winter and spring then pupate (pupae are the stage between larvae and adults) in early summer. Crane fly damage usually first appears during the dry days of summer as irregular patches. Grass dies because crane fly-damaged roots can't supply plants with water.
This brief life history points to two important periods when dealing with crane fly damage -- fall, when young larvae are starting to feed on roots, is the time to apply control measures, and mid-summer is when damage is likely to be seen.
For current crane fly control suggestions see our article at 'Bugs.