Definition:

Harp : The fore-wings of male mole crickets have a pair of large cells, the anterior of which is described as harp-shaped. The two cells together are called the stridulatory area. Females lack such large cells. In males, one of the veins on each wing is modified with a line of tiny teeth to form a stridulatory file. This file is drawn across a scraper on the other wing as the wings close, and makes a noise. Males make this noise - or "song"- by opening and closing the wings.