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a family of small butterflies resembling geometrids. The body is slender, and the wings are broad. The tips of the forewings are often elongate and falcate. The larvae have four pairs of abdominal legs; the tip of the abdomen is elongate, slightly raised, and pointed. The pupae hibernate. There are about 400 widely distributed species; most species inhabit the tropics. The USSR has 15 species. The larvae, which feed on the leaves of trees, are frequently forest pests.