2. I'TEEOPUS. 17 



more developed in the male than m the female, and corresponding to 

 the position of glands beneath. These glands secrete an oily sub- 

 stance on which the peculiar musky odour of the animals depends, 

 and which is remarkably abundant during the breeding-season. 



The fur of the adult male, especially that covering the back of 

 the head and neck, appears to be always more brightly coloured, 

 and the differently coloured portions of the fur contrast much more 

 strongly together than in the female of the same age*. But 

 although the colour of the tippet in the female is darker or less 

 brilliantly coloured than that of the male, it is rarely as dark as 

 that of the f nr of the back ; and this difference in colour between 

 the fur of the neck and that of the back is, perhaps, due to " pro- 

 tective mimicry ''f. 



The teeth of aU. the species agree in number and in general charac- 

 ters, but differ remarkably in certain species in relative development. 

 In most instances the premolars and molars are narrow, with an 

 external and internal cusp separated by a longitudinal groove, which 

 soon disappears with age (in some cases even before the animal 

 has attained maturity) by the internal cusp becoming worn down. 

 In Pt. leucopterus, Pt. aneiteanm, Pt. molossitms, and Pt. jubatus the 

 premolars and molars reach their greatest development, in the first- 

 named in general size, in the other three species in the presence of 

 additional basal cusps and ridges ; while in Pt. scapulatus and Pt. 

 macrofis these teeth are reduced to the smallest size known in the 

 genus, so that they resemble closely those of the genus Macroglossus. 

 Such differences in the development of the teeth are evidently due 

 to corresponding differences in the nature of the food ; for we find 

 the molar teeth reduced to the most rudimentary condition in 

 those species of the family which are known to feed on pulpy 

 fruits, such as the long-tx)ngued Macroglossi ; these, it may be 

 remarked, are inhabitants of the tropical parts especially of the 

 regions through which the Ptcropodidse are distributed, where soft 



* See the remarks on this in the writer's paper, " On Secondary Sexual 

 Characters in the Chiroptera," P. Z. S. 1873, p. 241. 



•f At first sight it might appear that this remarkable contrast of colours would 

 render the animal more conspicuous to passing enemies, and, consequently, more 

 subject to their attacks when hanging in an exposed position, as, for example, 

 from the branches of a lofty tree. But any one who has seen a colony of these 

 Bats suspended from the branches of a banyan tree or from a silk -cotton tree, 

 must have been struck with their resemblance to large ripe fruits , and this is 

 especially noticeable when they hang in clusters from the leaf-stalks of the 

 cocoanut-palm, where they may be easily mistaken for a bunch of ripe cocoa- 

 nuts. Hanging close together, each with his head bent forwards on the chest, 

 his body wrapped up in the ample folds of the large wings, and the back 

 turned outwards, the brightly-coloured neck and head are presented to the 

 view and resemble the extremity of a ripe cocoanut, with which the lai-ger 

 species of this genus closely correspond in size. 



It is worthy of note that this remarkable contrast in colour between the fur 

 of the neck and back is much less developed in the smaller species of the genus, 

 and not at all in the comparatively much smaller species of the other genera of 

 this family, whicli, by their small size, are less easily seen, and are enabled to 

 hide themselves in places inaccessible to the larger species. 



c 



