62 ENTOMOLOGICAL SOCIETY OF ONTARIO. 



apparently insignificant little beetle imported for the purpose from Australia will always 

 remain one of the most interesting stories in the records of practical entomology. 



The Vedalia has since been successfully colonized at the Cape of Good Hope and in 

 Egypt, and has produced the same results in each case. In Egypt the Vedalia was intro- 

 duced to prey upon an allied species of Icerya (/. cegyptiacitm, Douglas). We hope soon 

 to be able to send the same insect to India, where it has recently transpired that Icerya 

 (bgyptiacum occurs, while recent information received from Phra Suriya, royal com- 

 missioner of Siam at Chicago, would indicate that its introduction into Siam for the same 

 or a closely allied insect will be desirable in the near future. 



In fact, the success of the experiment was so striking and so important, and resulted 

 in the saving to California of an industry of so great a money value, that it has given rise, 

 not only in the popular mind but in the minds of a certain class of entomologists also, to 

 the idea that lemedial work against injurious insects should be concentrated upon this one 

 line of action, and that our best hope for their destruction lies with the parasitic and 

 predaceous species, not to mention fungus and bacterial diseases. From an extreme of 

 comparative incredulity the farmer and fruit-grower have gone, perhaps, to the other 

 extreme of too great faith. The case of Icerya and Vedalia, as I have frequently pointed 

 out, was exceptional and one which can not easily be repeated. 



One of the humorous phases of the Vedalia experiment is, that the wide newspaper 

 circulation of the facts — not always most accurately set forth -has brought me communi- 

 cations from all parts of the world asking for supplies of the renowned little Ladybird for 

 use against injurious insects of every kind and description, the inquiries being made, of 

 course, under a misapprehension of the facts. 



While this California experience thus afiorda one of the most striking illustrations of 

 what may be accomplished under exceptional circumstances by the second method of 

 utilizing beneficial insects, we can hardly expect to succeed in accomplishing much good 

 in this direction without a full knowledge of all the ascertainable facts in the case and a 

 due appreciation of the profounder laws of nature, and particularly of the interrelations 

 of organisms. Year in and year out, with the conditions of life unchaneed by man's 

 actions, the relations between the plant-feeder and the predaceous and parasitic species of 

 its own cla^^s remain suVistantially the same, whatever the fluctuations between them for 

 any given year ! This is a necessary result in the economy of nature ; for the ascendency 

 of one or the other of the opposing forces involves a corresponding fluctuation on the 

 decreasing side, and there is a necessary relation between the plant-feeder and its enemies 

 which, normally, must be to the slight advantage of the former and only exceptionally to 

 the great advantage of the latter. 



This law is recognized by all close students of nature, and has often been illustrated 

 and insisted upon by entomologists in particular, as the most graphic exempli6cations of 

 it occur in insect life, in which fecundity is such that the balance is regained with 

 marvellous rapidity, even after approximate annihilation of any particular species. But 

 it is doubtful whether another equally logical deduction from the prevalence of this law 

 has been sufiiciently recognized by us, and this is, that our artificial insecticide methods 

 have little or no eifect upon the multiplication of an injurious species, except for the 

 particular occasion which calls them forch, and that occasions often arise when it were 

 wiser to refrain from the use of such insecticides and to leave the field to the parasitic 

 and jivedaceous forms. 



It is generally when a particular injurious insect has reached the zenith of its increase 

 and has accomplished its greatest harm that the farmer is led to bestir himself to suppress 

 it, and yet it is equally true that it is just at this time that nature is about to relieve 

 him in striking the balance by checks which are violent and effective in proportion to the 

 exceptional increase of and consequent exceptional injury done by the injurious species. 

 Now the insecticide method of routing this last, under such circumstances, too often 

 involves, also, the destrucfion of the parasitic and predaceous species, and does more harm 

 than good. This is particularly true of those of our Coccidse and Aphididte and those of 

 our Le|>idopterous larvie which have numerous natural enemies of their own class ; and 

 it not only emphasizes the importance of preventive measures, which we are all agreed to 

 urge for other cogent reasons, and which do not to the same extent destroy the parasites, 



