1923- The Balance of Nature. 113 



THE BALANCE OF NATURE. 



The danger of turning loose foreign animals and of 

 introducing foreign plants into any country has often been 

 pointed out ; and almost as frequently the danger has 

 been proved up to the hilt by practical experiments. The 

 Scotsman who thought it would be nice to have a thistle 

 to keep him company when he went to Australia and the 

 man who introduced the Rabbit into the same continent 

 are two well known, and no longer honoured, experimenters ; 

 while the case of the Grey Squirrel at Castle Forbes referred 

 to by Mr. Watt, p. 95 ante, is another case in point. Indeed 

 one has merely to open any book dealing with economic 

 zoology to obtain numerous proofs of the dangers attending 

 such introductions. 



The following is a good example : — " It appears to 

 have been accidently introduced into New England some 

 seventeen years ago on rose bushes from France. Since 

 then it has rapidly spread and has not only caused damage 

 over a large tract of country, but appears to be still on 

 the increase." ^ 



There is, moreover, another and quite different reason 

 for objecting to such introductions, namely that in almost 

 every country nowadays there is a body of naturalists 

 engaged in working out its fauna and flora and the 

 distribution thereof, and for any person to introduce a 

 foreign species — or worse still a native species which has 

 a restricted range in another district — can only tend to 

 render more complicated the already very difficult labours 

 of the students of distribution. Accidental introductions 

 cannot always be avoided, but it seems strange to the 

 writer that members of a learned Society in Ireland should 

 be guilty of such a thing. 



A friend who recently visited the Zoo at Dubhn was 

 naturally interested in the Lepidoptera larvae which are 

 being exhibited there and he asked the attendant what 



1 Vide Theobald : Insect Pests of Fruit, p. 22, under the Brown Tail 

 Moth. 



