HABITS. 251 



is observed occasionally at dusk during the autunni 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 biing 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 (Vesperugo nodivagans), M'hich ranges as far north as 

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

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

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

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

 seems to afibrd perfectly conclusive evidence of the migratory habits of the 

 particular species to which they belong. 



In regard to their geograpliical distribution, it may be observed 

 Distribution. , , * „ , , xi i 1 it " ■ , 



that liats are louml over ahiiost tlie whole world ; one .species at lea.st 



even extending as far northwards as the Ai-ctic cii'cie. 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, tlie 



bats, according to Mr. \V;dlace, may be regai'ded as some of the most characteristic 



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



only to that held by tlie apes, monkej's, and lennirs, 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 tliose 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 finiit-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 



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



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



particular di.stricts 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 li.st published in 1878, Dr. Dob.son recognised no less than four 



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



flate 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 they are still designated in certain parts of the country, conveys a very 



accurate notion of their zoological p)Osition, if we use the term mouse in the popular 



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



