8 THE COMMON RATS 



found, the melanic form of Mus rattus (or Mus rattus rattus, 

 Millais) the 'black' rat, is more frequent in the colder latitudes, 

 and Mus rattus alexandrinus (Millais) the gray form (the 'roof 

 or 'snake' rat) in the warmer latitudes, but the two are not 

 sharply segregated. At the same time both of these seem more 

 dependent on warmth, or more resistant to it, than the Norway 

 rat. 



Although we shall have little to say in the following pages 

 about Mus rattus, yet it is desirable to give its history in order 

 to obtain the proper setting for Mus norvegicus, at present the 

 dominant species. The geological evidence just given indicates 

 the very early appearance of the house rat in Europe but our 

 records of its migrations all fall within the present era. 



The history of the early migrations is of necessity vague and 

 incomplete, and even in the later times when dates are given it 

 must be remembered that such animals might have been present 

 for some time without appearing in numbers sufficient to cause 

 comment. 



There is no good evidence that the Greeks or Romans before 

 the present era were familiar with the rat as a pest, and there- 

 fore, even if present, it was probably not abundant at that 

 period on the shores of the Mediterranean. 



The history of the house rat from the earliest times to the 

 eleventh century makes an interesting archaeological study, but 

 the conclusions which may be drawn from the scanty records 

 and indefinite allusions are too uncertain to be of value for our 

 present purpose and we therefore pass directly to the later 

 authors. 



Possibly as far back as the migration of the hordes (Volker- 

 wanderung, 400-1100 A. D.) and later in consequence of the 

 increasing use of trade routes with the East, the house rat en- 

 tered western Europe in appreciable numbers (Hehn, '11). It 

 is reported to have arrived there after the twelfth century (Kel- 

 ler, '09, citing Theodoros Prodromos). Giraldus Cambrensis,^ 

 (1146?-1220) records several anecdotes concerning it. 



^ Albertus Magnus (d. 1280) is sometimes cited as having mentioned the black 

 rat. This is not correct. A. de I'lsle (1865) has pointed out that the description 

 in question applies to the dormouse— Mj'oxus quercinus. 



