Jawed vertebrates are typified by paired appendages, fins or legs, which may be secondarily lost. This trait is characteristic of secondarily aquatic vertebrates with flippers. Moreover, the reward system is differentially activated by the primary pheromones and secondarily attractive odorants. Plastrons are organs that some arthropods evolved secondarily to breathe air underwater. Embryophytes are primarily adapted for life on land, although some are secondarily aquatic. Chlorantraniliprole is active on chewing pest insects primarily by ingestion and secondarily by contact. Cysts rarely cause any symptoms, unless they become secondarily infected. Other causes that can secondarily produce parkinsonism are stroke and drugs. Oca-growing communities often name varieties based primarily on tuber morphology and secondarily on flavor. Most adult insects have wings (excepting where secondarily lost) and functioning reproductive organs. The lesion then ulcerates and may become secondarily infected with bacteria. That responsibility lies primarily with the states and secondarily with Congress. Many Arab-Berbers identify primarily as Arab and secondarily as Berber. The high bacterial load in the mouth means that ulcers may become secondarily infected. Secondarily unilocular taxa evolved during the Jurassic and Cretaceous.