Order Chiroptera - Family Vespertilionidae Author Wilson, Don E. Author Reeder, DeeAnn text 2005 The Johns Hopkins University Press Baltimore Mammal Species of the World: a Taxonomic and Geographic Reference (3 rd Edition), Volume 1 451 529 book chapter 0-8018-8221-4 10.5281/zenodo.7316519 Pipistrellus (Pipistrellus) hesperus H. Allen 1864 Pipistrellus (Pipistrellus) hesperus H. Allen 1864 , Smithson. Misc. Coll., 7: 43 . Type Locality: USA , California , Imperial Co., Old Fort Yuma. Vernacular Names: Western Pipistrelle . Subspecies: : Subspecies Pipistrellus (Pipistrellus) hesperus subsp. hesperus H. Allen 1864 Subspecies Pipistrellus (Pipistrellus) hesperus subsp. maximus Hatfield 1936 Distribution: Washington to SW Oklahoma ( USA ), and Baja California , south to Hidalgo and Guerrero ( Mexico ). Conservation: IUCN 2003 and IUCN / SSC Action Plan (2001) – Lower Risk (lc). Discussion: Subgenus Pipistrellus . See Hall (1981) . Placed in Hypsugo by Koopman (1993) , but here retained in Pipistrellus pending further study.