610 MURIDAZ—EPIMYS 
New Statistical Account of the Parish of Newlands, Peeblesshire, 
1834, 137; the date of its arrival in Morayshire is given as about 1814 
by the Rev. G. Gordon. 
We have no certain information as to the date of its introduction 
to Ireland, but this probably happened soon after the arrival of the 
species in England. Rutty (Wat. Hist. of Dublin, i., 281) says, however, 
that it “first began to infest these parts about the year 1722.” 
The species first arrived in the United States of America, probably 
from England, about the year 1775; according to Audubon it was still 
unknown from the Pacific coast in 1851, although its introduction must 
have occurred there soon afterwards (Lantz, The Brown Rat in the 
United States, 1909, 13). 
The success of this animal as a colonist seems largely dependent 
upon temperature and climate; but the abundance or scarcity of food, 
the presence or absence of suitable shelter, and the nature of the 
competition to be faced, are doubtless factors of equal importance in 
governing the distribution of this, as well as of other species. It has 
therefore met with varied fortune in the many lands it has invaded. 
In India, where the vattus group is at home, the foothold of xorvegzcus 
appears insecure ; its colonies do not spread far from the landing places, 
and it seems wholly incapable of displacing the native rats.1 In warm 
temperate countries, like Italy and Spain, it has acquired a good 
footing, but is forced to share the land with the “wild-coloured” 
sub-species of vattus. In temperate Europe its success has been 
marked; it has spread everywhere and has practically ousted vattus. 
Similarly on its arrival in New Zealand it promptly extirpated “ Mus 
maoritum,’ Hutton, ze, the descendant of the vattus stock previously 
introduced by Europeans. In Switzerland its progress has been slow; 
it appears to have entered from Germany across the Rhine and Lake 
Constance, and by 1869 had become common in some of the central 
Swiss cities, as Berne and Lucerne; but although at that time known 
from many towns and several cantons, it had nowhere 'risen to any 
notable height in the mountains; and Fatio doubted whether it was 
established then at Geneva, where the va¢tus group still predominated. 
In Sweden and Norway it has almost completely displaced raztus, 
but its range shows limitations similar to those of its predecessor, 
and it is scarce in the most northerly districts. In Norway its advance 
is said, by Collett, to be slow; it seems unable to colonise the upper 
parts of the main valleys, and is lacking from the floors of all the 
tributary valleys; it is still scarce or wanting in many of the coastal 
districts and inhabited islands. In northern Norway it occurs only in 
buildings or in certain market places, as at Troms6 and Hammerfest, 
1 Bonhote (Proc. Zool. Soc., 1910, 65) says, however, that norvegicus is gradually 
increasing in East India and Egypt at the expense of va¢/us and other rats. 
