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Bulletin American Museum of Natural History. [Vol. XXXVII, 



act as highly sensitized organs. They seem to feel and in reality must be 

 able to measure certain waves, so that it appears as if they could see and hear 

 with them as well. The experiments of Spallanzani have shown that even 

 if blinded they will not strike in flight against any solid object except when 

 thoroughly exhausted. When chasing them in closed rooms, we often have 

 seen them escape in full flight and apparently unhampered by narrow slits 

 in the windows and doors through which we thought they could hardly 

 crawl. Dobson believed that long-eared or leaf -nosed bats prefer dark- 

 ness, but the Megadermidse, with the largest nose-leaves and ears, are semi- 

 diurnal; the Nycteridse, with these appendages still fairly elaborate, we 

 found to be rather crepuscular. Yet Taphozous with no nose-leaves at all, 

 generally hung in relatively light places throughout the day, and was one 

 of the last to fly out. Their behavior depends evidently on feeding-habits 

 or on the abundance of their victims at such hours. 



At Farad je where Taphozous mauritianus was common we found great 

 numbers of moth-wings beneath places where they were accustomed to rest. 

 These evidently were habitually rejected before feeding. 



The interfemoral membrane, really their third sail (p. 516), is well 

 developed in all African families of Microchiroptera, except in the Rhino- 

 pomidse. It undoubtedly increases the steering facilities which, by stretch- 

 ing out or pulling in the limbs or shifting the tail, play such an important 

 part in the capture of insects, all of which have their own peculiarities of 

 flight. The full stomach of bats shot on the wing furnish evidence that 

 their erratic flight cannot be entirely ascribed to their inability to progress 

 with ease. On the contrary, we are prompted to look upon their meander- 

 ings as an exhibition of great dexterity where flight of any kind is but the 

 means to a successful end. Entomologists, who will remember how often 

 they looked longingly after an insect that they endeavored to capture in 

 full flight, are probably the most qualified and willing to assent to such a 

 statement. 



Secondary sexual differences amongst insectivorous bats" are far more 

 varied than in fruit-bats. They are however much less conspicuous and 

 depend mostly on specific characteristics. Under these circumstances we 

 find it best to refer to the field notes, where we have pointed out all those 

 that came to our attention. These are: 



1, the larger gular pouches of the males of Taphozous mauritianus (p. 513) ; 



2, the larger size of females of Saccolaimus peli (p. 515) ; 



3, the dorsal glands in males of Laviafrons affinis (p. 520); 



4, the possession of a frontal sac and abdominal appendages in Hipposi- 

 deros caffer (p. 524); 



5, the curious anal sacs of Hipposideros langi (p. 526) ; 



