(Pachycereus schottii)
Lophocereus schottii (Synonyms: Pachycereus schottii), the senita cactus, is a species of cactus from southern Arizona and north-western Mexico, particularly Baja California and Sonora. Synonyms include Pilocereus schottii and Pachycereus schottii. The senita cactus exhibits mutualism with the senita moth. The senita moth is the only nocturnal pollinator of the cactus, and the moth relies on the cactus as a host for reproduction. Pachycereus is a genus of 9–12 species of large cacti native to Mexico and just into southern Arizona, United States. They form large shrubs or small trees up to 15 m tall, with stout stems up to 1 m in diameter. Pachycereus comes from the ancient Greek (pachys) meaning "thick" and the Latin cereus meaning "torch".