(Temminck, 1840)
Least Pipistrelle; Indian Pygmy bat
External characters (Table 94)
This is the smallest pipistrelle (Pmi1) found within the subcontinent with an average forearm length of 27.7 mm (25.0-30.2 mm). However, it is not possible using external characters alone to discriminate between this species and smaller individuals of P. coromandra (Pco1) even when the two occur at the same locality (it is possible using cranial characters). In general, as in P. coromandra the dorsal pelage is a uniform brown, varying in tone from mid-brown to a deep clove brown (Pmi2). The ventral surface is paler; the hair tips are buffy brown; the roots are dark brown or black. The ears and membranes are dark throughout and essentially naked. Body weight averages about 2 grams (Gopalakrishna and Karim, 1972). The baculum has a long thin shaft and a distinctly bifid tip; the basal lobes are well developed and deflected ventrally (Fig. 205).
Cranial characters
The skull, with an average condylo-canine length of 10.2 mm (9.3-10.7 mm) is significantly smaller than that of P. coromandra . The palate (M3-M3) is noticeably narrower: 4.9 mm (4.5-5.2 mm) as compared to 5.5 mm (5.0-6.0 mm). The postorbital constriction is relatively broad but the braincase is small.
Dentition
- Upper toothrow length (C-M3) averages 3.8 mm (3.5-4.1 mm) as compared to 4.4 mm (3.9-4.6 mm) in P. coromandra . The first upper incisor (I2) is bicuspidate with the secondary cusp usually about half the height of the principal one. The second incisor (I3) is well developed, it exceeds the secondary cusp of the first incisor in height; it is separated from the upper canine by a narrow diastema. The upper canine has a distinct posterior secondary cusp. The first upper premolar (PM2) is intruded from the toothrow; it is about equal in crown area to the first upper incisor (I2). The canine and the second premolar (PM4) are not in contact but are closely adjacent.
- The first lower premolar (pm2) is slightly extruded from the toothrow; it is three-quarters the crown area and about two-thirds the height of the second (pm4).
Karyology
2n=38, FN=48 with 12+X metacentrics and 24+Y acrocentrics (Pathak and Sharma, 1969. However, Bhunya and Mohanty, 1975 report a different chromosomal formula: 2N= 42, with 24+X metacentrics, 2 submetacentrics and 14+Y acrocentrics.
Variation
The taxon glaucillus from the Punjab was differentiated from mimus from Gujarat on the basis of colour (bistre brown versus mouse-grey). However, pelage colour varies considerably even between individuals from the same colony and therefore all specimens from the Indian subcontinent are here referred to P. t. mimus (Sinha, 1980).