Issidae is a family of planthoppers described by Spinola in 1839, belonging to the order Hemiptera, suborder Auchenorrhyncha superfamily Fulgoroidea. Species of this family are present throughout the Northern Hemisphere. In 2013, scientists described a biologically unique set of mechanical gears in an Issus nymph, though identical structures are known in most planthoppers, and were known for decades before the function of the gears was discovered