leather jacket
n.— «The female crane fly lays her eggs in the soil, usually around water or in mud. When the eggs hatch if the soil is too hard the larvae, or leather jackets as they are called, aren’t able to reach the surface.» —“Blistering summer caused crane fly invasion” by Frances Earlam Wirral Globe (Birkendhead, England, United Kingdom) Oct. 3, 2006. (source: Double-Tongued Dictionary)