Crane fly larvae feed on the roots of grasses. Usually very little damage is done as plants have a remarkable ability to compensate for minor root damage. However, when populations are high (estimated to be about 25-30 larvae per square foot) damage to turf areas can be extensive. (Note: One property in the Eastbridge area had 75-125 larvae per square foot)!
The adult crane fly is found in the late summer and early fall. It has long legs and looks very much like a large mosquito (the body alone is about 1" long). One common name for these insects is "mosquito-hawk". The adults are harmless. They do not bite nor do they attack mosquitos. They are very common at night around lights.
Larvae, sometimes called "leather jackets," live in the soil. Larvae hatch from eggs laid in the late summer. They feed during the fall and into the spring of the following year. They stop feeding in May. Damage generally starts to be noticeable during the spring, caused by feeding that occurred the previous fall and winter. Damage can also occur when birds scratch at the lawn surface attracted to larvae. Birds are important predators of crane fly larvae and great care should be taken not to poison birds if insecticides are used.
Now that European crane fly has arrived, it is likely to be a permanent inhabitant of our lawns. Severely damaged lawns may need renovation. It is probably not necessary to treat these lawns with insecticides prior to renovation as normal site preparation (tilling and rotovation) controls larvae.