VOL. I.] The Economy of Nature. 37 



the means applied by nature herself to restore the equilibrium, in 

 other words to counteract the harm resulting from an inordinate 

 prevalence of the injurious species. These means we have to imi- 

 tate, as far as an imitation of thein is in our power, and carefully 

 abstain from producing new disturbances by the use of violent rem- 

 edies, because the history of these experiments, where it dates 

 farther back than in our own country, has demonstrated that the ben- 

 efit derived from violent interference is of short duration, and even 

 then frequently of a very questionable nature, and that a series of 

 other disturbalTces is always the result. I quote here a historical 

 example: 



At the beginning of this century the orchards of Normandy, 

 Belgium and other districts of Northern Europe were afflicted by a 

 kind of Psylla. As cider is one of the staple products of that region 

 the matter excited considerable attention, and a wash, chiefly con- 

 taining lye, was applied, and proved a perfect success. The next 

 year the grain fields suffered considerably from the green aphis, 

 which, as it was a warm and moist summer was imputed to that cir- 

 cumstance, but as the aphis increased for two years independently 

 of the weather, and the apple trees became infested also by different 

 kinds of borers more than ever before, the scientists at the univer- 

 sities of the different countries were consulted, and their investiga- 

 tions proved that the application of the lye had killed, besides the 

 Psylla, the Coccinella and other enemies of the injurious insect, 

 had driven away the insect-feeding birds, and in this way facilitated 

 the multiphcation not only of the insect-feeding parasites of the 

 apple tree, but of insects injurious to vegetation in general. 



I am glad to see that our biological authorities begin to follow the 

 advice given by nature, and introduce insects of the Coccinella tribe 

 from Australia, This of course would not have been necessary if 

 they had protected our native species, formerly common and now 

 very rare, I think it not out of place to warn our horticulturists 

 not to combine the two systems and treat the Australian newcomers 

 to a course of washes, or else a new expedition to Australia may 

 become necessary. 



