HABITS. 251 



is observed occasionally at dusk during the autumn months hawking about 

 according to its nature in search of insects ; but as it is never seen except at that 

 particular season, it is clear that it is not a resident, but merely blown across the 

 ocean by those violent north- west gales which also usually bring numbers of birds 

 from the American continent. The hoary bat is, however, not the only species in 

 which there is evidence of periodical migrations. Thus Dr. Merriam tells us that 

 the silver-haired bat (Vesperuyo noctivagans), which ranges as far north as 

 Hudson's Bay, is known to visit every spring and autumn a solitary lighthouse 

 situated on a solitary rock off the coast of Maine, fifteen miles from the nearest 

 island and thirty miles from the mainland. This rock being uninhabited per- 

 manently by bats, the occurrence of these stray individuals at the spring and fall 

 srrms to afford perfectly conclusive evidence of the migratory habits of the 

 particular species to which they belong. 



In regard to their geographical distribution, it may be observed 

 that bats are found over almost the whole world ; one species at least 

 even extending as far northwards as the Arctic circle. They are far more abundant 

 within the tropics and the warmer parts of the temperate zones than elsewhere ; 

 and it is to those regions alone that the larger species are restricted. Indeed, the 

 bats, according to Mr. Wallace, may be regarded as some of the most characteristic 

 of the Mammals of the tropical zone, occupying in this respect a position second 

 only to that held by the apes, monkeys, and lemurs, and becoming suddenly much 

 less plentiful, both as regards the number of individuals and of species, when we 

 pass into the temperate zone, and still more reduced in both respects when we reach 

 the colder parts of those regions. 



In some instances particular family groups of bats are confined more or less 

 exclusively to particular regions of the earth's surface ; although others enjoy an 

 almost world-wide distribution. For instance, while the fruit-bats are entirely 

 confined to the warmer regions of the Old World, and the vampires and their 

 allies to America, some of the more common types of ordinary European bats, like 

 Vesper uyo and Vespertilio, are almost cosmopolitan. It will be found that these 

 cosmopolitan forms belong to the more generalised types, while those restricted to 

 particular districts are usually the more specialised form. It is somewhat curious 

 that, according to Dr. Dobson, bats are quite unknown in Iceland, St. Helena, 

 Kerguelen, and the Galapagos Islands. 



The number of species of bats known to science is now enormous. 

 Numbers. 



In a list published in 1878, Dr. Dobson recognised no less than four 



hundred distinct species, arranged in eighty genera, and six families. Since that 

 date the number has, however, been so largely increased, that we shall probably be 

 not far wrong in setting it down as but little, if at all, short of four hundred and 

 fifty. With such a portentous list to deal with, it will be obvious that, in a work 

 like the present, all that can be attempted is to indicate some of the more generally 

 interesting and leading types, leaving the others for technical treatises. The old 

 English name Flittermouse, by which these animals were known to our ancestors, and 

 by which the5 7 are still designated in certain parts of the country, conveys a very 

 accurate notion of their zoological position, if we use the term mouse in the popular 

 signification, in which it embraces animals like the shrews, as well as the true mice. 



