قراءة كتاب A Synopsis of the American Bats of the Genus Pipistrellus
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A Synopsis of the American Bats of the Genus Pipistrellus
bb">Accessory cusp present on anterointernal face
(Synonomy under subspecies)
Range.—Arid Sonoran life-zones of western North America from Washington southward to Jalisco.
Characters.—Smoke Gray to Buff Brown (Capitalized color terms after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912) dorsally; total length, 60 to 86; foot less than half as long as tibia; tragus blunt with terminal part bent forward; skull nearly straight in dorsal profile; inner upper incisor unicuspidate; outer upper incisor with accessory cusp on anterointernal face; P1, viewed from occlusal face, less than a seventh of area of canine, and from labial aspect concealed by canine and fourth premolar; lower, third premolar lower than anterior cusp of canine; lower premolars crowded, distance between canine and first molar less than length of second lower molar.
Remarks.—In the United States and in the northern part of Mexico, P. hesperus is the smallest bat found. Little is known about its habits. It emerges earlier in the evening than other species of bats. The frequency with which it is seen near cliffs suggests that it finds concealment under rocks. In winter, in Nevada (Hall, Mammals of Nevada, p. 150, 1946), P. hesperus has been found singly in crevices in the roofs of mine tunnels.
In the United States National Museum in July, 1949, the specimen providing the easternmost record station of occurrence was examined by us. This is No. 23591, in alcohol, taken on August 24, 1890, by William Lloyd, original No. 88, at the mouth of the Pecos River in Texas. In the same collection there is a specimen of Pipistrellus subflavus providing the westernmost record of occurrence of that species. This specimen, a skin with skull, is No. 126729, ♂, taken on May 3, 1903, by Jas. H. Gaut, original No. 1271, at Comstock, Texas. The two localities concerned are in the Valley of the Rio Grande, and are only about five miles apart. Nevertheless, the two specimens are clearly referable to their respective species and show no tendency toward intergradation. Consequently, confidence is felt in treating Pipistrellus hesperus and Pipistrellus subflavus as two distinct species.
The most recent report upon geographic variation throughout the entire species, Pipistrellus hesperus, was that by Hatfield (Jour. Mamm., 17:257-262, August
