Pipistrellus hesperus australis Miller, N. Amer. Fauna, 13:90, October 16, 1897.
Pipistrellus hesperus apus Elliot, Field Columb. Mus., pub. 90, zool. ser., 3:269, March 8, 1904. Type from Providencia Mines, Sonora, Mexico.
Type locality.—Barranca Ibarra, Jalisco, Mexico.
Range.—Central Arizona south to Jalisco and including the southern half of Baja California. Marginal occurrences (after Hatfield, op. cit.: 261, unless otherwise indicated) are: Arizona: Camp Verde; Fort Bowie. Sonora: Pilares (Burt, Miscl. Publ., Mus. Zool., Univ. Michigan, 39:24, 1938). Jalisco: Barranca Ibarra (Miller, orig. descr.). Baja California: Miraflores; San Ignacio. Arizona: Bates Well.
Diagnosis.—Size small for the species; total length, 67.1(60-72); tibia, 11.3(10.1-12.3); forearm, 28.4(26.3-30.0); greatest length of skull, 11.7(11.3-12.0); breadth of braincase, 6.1(5.9-6.3). Color: between Cinnamon Drab and Drab, dorsally; Wood Brown to Light Drab, ventrally (after Hatfield, op. cit.:260).
Remarks.—Hatfield (op. cit.) examined no specimens from Mexico (Baja California excepted) and Burt (op. cit.) who did examine some specimens (from Sonora), referred one from northwestern Sonora to [P. h. hesperus] and those from northeastern Sonora to [P. h. merriami]. Since our treatment of subspecies of Pipistrellus ([P. s. veracrucis] excepted) aims merely to reflect the latest systematic treatment accorded the animals, we would follow Burt (op. cit.) were it not for the fact that he shows the geographic range of [P. h. merriami] separated by the range of [P. h. hesperus] into two parts. This is inconsistent with the ordinarily accepted concept of subspecies. Consequently, we have followed Hatfield (op. cit.). Clearly, a critical study is needed of adequate material of [Pipistrellus hesperus] of Mexico.
Pipistrellus hesperus maximus Hatfield
Pipistrellus hesperus maximus Hatfield, Jour. Mamm., 17:261, August 14, 1936.
Type locality.—Dog Spring, Hidalgo County, New Mexico.