Crane flies are large, flying insects that are sometimes mistaken for large mosquitoes. Adult crane flies do not bite or spread diseases like mosquitoes, and pose no threat to humans. However, the larvae feed in the soil and can be quite destructive to lawns and turf. Though a healthy lawn can usually tolerate a moderate number of crane flies, if too many larvae are present they can quickly cause significant damage to the grass. Adult crane flies emerge in late summer, mate and lay eggs within a day or so, and then hatch into “leatherjackets” (larvae). The larvae feed primarily underground in the fall and again in the spring after overwintering in the soil. They then pupate in the soil in mid spring.