Distribution.—Western México; known certainly from south-western Durango south to southern Jalisco (see Fig. 1).
Diagnosis.—Size small both externally and cranially (forearm in adults 40.4-44.1 mm., greatest length of skull 21.7-22.9); rostrum short and abruptly elevated; skull relatively broad; dorsal pelage drab brownish over-all, usually lacking epaulets (pale yellowish brown when present); ventral pelage brownish gray.
Comparisons.—From Sturnira ludovici ludovici, the only other subspecies of the species, S. l. occidentalis differs in averaging smaller in most external and cranial dimensions (in some measurements the upper size limits of occidentalis barely overlap the lower limits in specimens of ludovici examined), in having a relatively broader skull with a shorter, more abruptly elevated rostrum, and in being paler both dorsally and ventrally.
From Sturnira lilium parvidens, with which it is sympatric, S. l. occidentalis usually (but not always) differs in being brownish (rather than yellowish to yellowish orange) dorsally and in lacking epaulets, and differs in the following cranial features: first upper incisors simple (rather than weakly bifid in unworn condition), larger, and more nearly straight when viewed from the front; second upper incisors reduced; lower incisors bilobate rather than trilobate; lingual cusps on m1 and m2 greatly reduced; M2 usually turned inward from M1 at distinct angle. The two species have approximately the same external and cranial dimensions in western México.
Measurements (in millimeters).—External measurements of the holotype are as follows: total length, 58; length of hind foot, 15; length of ear, 18; forearm (average of both), 42.5. Corresponding average and extreme measurements of 11 adults from 4 km. N Durazno, Jalisco, followed by those of eight adults from 17 km. SE Talpa, Jalisco, are: 61.9 (59-65), 60.9 (57-68); 14.1 (12-15), 13.0 (13); 16.1 (15-18), 16.0 (15-17); 42.2 (40.4-43.8), 42.9 (41.6-44.1); weight in grams, 16.8 (15-19, six specimens only), 19.2 (16.3-22.5).
Cranial measurements of the holotype additional to those given in Table 1 are: condyloincisive length, 19.7; breadth across upper canines, 5.5; length of mandibular tooth-row (c-m3), 6.7.
Remarks.—The pattern of geographic variation in size in Sturnira ludovici resembles that in many other species of tropical bats in North America in that individuals from the northern parts of the range are smaller than those from the south. Mexican specimens herein assigned to S. l. ludovici average somewhat smaller than specimens from Central America and the northern part of South America (but are within the currently understood size limits of that subspecies) and average paler as well. Additional material is needed from central and eastern México before the limits of distribution of the two subspecies of ludovici can be determined accurately.
All specimens examined of the new subspecies were trapped in mist nets. The holotype was captured in a net stretched across an old road among large fruit trees situated along a small river (a tributary of the Río del Baluarte). Tropical deciduous vegetation grew in the narrow valley of the river but the adjacent hills supported oak. A specimen of Artibeus jamaicensis jamaicensis was netted along with the holotype and on the previous night, August 30, one individual each of Glossophaga soricina leachii and Sturnira lilium parvidens were taken in the same net. Baker and Greer (1962:69) also reported the two species of Sturnira as netted together 6 mi. S Pueblo Nuevo in adjacent Durango.
Table 1.—Some Measurements of Adults of Two Subspecies of
Sturnira ludovici.
| Number of specimens averaged, or catalogue number, and sex | Length of forearm | Greatest length of skull | Zygomatic breadth | Mastoid breadth | Interorbital constriction | Length of maxillary tooth-row | Breadth across upper molars |
| Sturnira ludovici occidentalis, holotype | |||||||
| 92798 KU, ♀ | 42.5 | 22.0 | 12.5 | 11.4 | 5.3 | 6.1 | 7.5 |
| ½ mi. W Revolcaderos, Durango | |||||||
| 5698 MSU, ♀ | 43.7 | 22.6 | 13.1 | 11.9 | 6.0 | 6.3 | 7.8 |
| 5699 MSU, ♀ | 42.3 | 22.2 | 12.7 | 11.3 | 5.6 | 5.9 | 7.5 |
| 17 km. SE Talpa, Jalisco | |||||||
| Average 8 (4 ♂, 4 ♀) | 42.9 | 22.5 | 12.9 | 11.5 | 5.9 | 6.2 | 7.7 |
| Minimum | 41.6 | 21.7 | 12.6 | 10.9 | 5.7 | 6.0 | 7.5 |
| Maximum | 44.1 | 22.9 | 13.5 | 11.8 | 6.3 | 6.4 | 7.9 |
| 20 km. WNW Purificación, Jalisco | |||||||
| 92811 KU, ♂ | 42.0 | 22.6 | 13.2 | 12.0 | 6.0 | 6.2 | 7.7 |
| 4 km. N Durazno, Jalisco | |||||||
| Average 11 (1 ♂, 10 ♀) | 42.4 | 22.5 | 13.0 | 11.4 | 5.8 | 6.2 | 7.7 |
| Minimum | 40.4 | 21.8 | 12.6 | 10.8 | 5.3 | 5.8 | 7.5 |
| Maximum | 43.8 | 22.9 | 13.4 | 11.8 | 6.1 | 6.3 | 8.0 |
| Sturnira ludovici ludovici, 10 mi. SW Villa Juárez, Puebla | |||||||
| 67399 KU, ♀ | 44.2 | 24.0 | 13.3 | 11.8 | 5.9 | 6.4 | 8.1 |
| 67400 KU, ♀ | 42.9 | 23.2 | 13.7 | 11.9 | 6.0 | 6.3 | 8.1 |
| 11 km. W Quiroga, Michoacán | |||||||
| 95703 UMMZ, ♂ | ..... | 23.5 | 13.5 | 11.6 | 5.9 | 6.2 | 7.6 |
| 95704 UMMZ, ♀ | ..... | 23.0 | 12.8 | 11.0 | 5.7 | 6.3 | 8.0 |
| Vista Hermosa, Oaxaca | |||||||
| 91635 KU, ♀ | 45.1 | 23.9 | 13.4 | 11.8 | 6.0 | 6.5 | 8.0 |
| 91636 KU, ♀ | 46.0 | 23.6 | 13.1 | 11.9 | 5.7 | 6.7 | 8.0 |
| La Cruz Grande, La Paz, Honduras | |||||||
| 126791 AMNH, ♀ | 44.0 | 23.6 | 13.5 | 11.8 | 6.1 | 6.3 | 8.1 |
| 126811 AMNH, ♀[1] | 45.5 | 24.6 | 13.2 | 12.0 | 6.3 | 7.2 | 8.2 |
| Sierra Negra, Sierra de Perijá, Colombia (after Hershkovitz, 1949) | |||||||
| Minimum (2 ♂, 2 ♀) | 44.2 | 22.9 | 13.2 | ..... | 6.2 | 6.5 | ..... |
| Maximum | 46.0 | 24.2 | 13.8 | ..... | 6.7 | 7.0 | ..... |
| near Gualea, Ecuador | |||||||
| 67328 AMNH, ♂[2] | ..... | 25.0 | 14.0 | 12.4 | 6.3 | ..... | 8.4 |
| 67329 AMNH, ♂ | 45.3 | 24.9 | 13.9 | 12.2 | 6.1 | 7.0 | 8.4 |