176 



THE CANADIAN HORTICULTURIST. 



How tnwy it he 'prevented ? It may 

 be prevented by applying to the plant 

 or to the soil, certain odorous sub- 

 stances which are popularly believed to 

 be disagreeable to the insect, and there- 

 fore, to drive it away. 



Among these substances may be 

 mentioned kerosene oil, coal-tar, naph- 

 thaline, carbolic acid, gas-lime, and 

 bisulphide of carbon. That these and 

 similar substances have been success- 

 fully used in preventing insect attack, 

 is undeniable, resting as the claim does, 

 on authoritative testimony, which T 

 would be glad to present to you if there 

 •were the time. 



How do they prevent the deposit % 

 The answer to this question is the object 

 of the present paper. The views that 

 I shall present are my own — original, 

 so far as I know. They have been but 

 recently conceived, without the time or 

 opportunity of maturing them. They, 

 as yet, may only claim theoretic value, 

 but believing as I do, not only in their 

 correctness, but that they are destined 

 to be of eminent service to economic 

 entomology, I esteem it a privilege to 

 offer them first to this Society. I do 

 so from the deep interest which you 

 feel in entomological investigations, as 

 shown in the admirable papers that 

 have been presented at former meetings, 

 in the jjrominent place you have given 

 to entomological topics in your discus- 

 sions, and in the invitation extended 

 to your State Entomologist, to ad- 

 dress you at this time. And beyond 

 these considerations, there is the fact 

 that your membership offers all needed 

 opportunity for testing these views, 

 and I am sure that there is the willing- 

 ness to take the pains requisite for their 

 proper test. 



In answering the question, how do 

 these odorous substances, in their appli- 

 cation, prevent the deposit of eggs, I 

 must first premise, that much the larger 



proportion of the insect world are 

 guided in the deposit of their eggs, not 

 by the sense of sight, but by the sense 

 of smell. Allow me a consideration of 

 this view, before proceeding to its 

 practical application. The idea is a 

 popular one, that most of the moths and 

 beetles and many of the insects that 

 attack vegetation, select by means of 

 sight the particular plant upon which 

 to place their eggs. Their marvellous 

 compound eyes, consisting of hundreds 

 and even thousands of separate lenses, 

 even to the number of 34,000, as in the 

 eye of the butterfly, have been cited as 

 a wonderful provision in nature, to 

 afford that acuteness of vision which 

 was needed in their selection of the 

 proper plant on which to oviposit. 

 While sharing, in this belief, I had 

 often wondered at the incomprehensible 

 acuteness shown by an insect in the dis- 

 covery of the particular species of yjlant 

 upon which alone the young caterpillars 

 proceeding from its eggs, could feed, — 

 in the discovery of a single individual 

 of a rare species occurring in a certain 

 locality, and growing in such a manner 

 as effectually to hide it from human 

 observation. When its range of food 

 plants extends beyond a species to all 

 the members of a genus, how could it 

 detect all of the often greatly different 

 forms? When a still broader range 

 embraces the several genera of an ex- 

 tended order, a still greater variety 'of 

 forms are presented, which the rude 

 ins€>ct brain must group and classify, 

 and claim within its province. How 

 amazing such knowledge without pre- 

 vious instruction. It had no parents 

 living, as in the class of vertebrates, 

 which might teach it by example. It 

 had no ancestors a whit wiser than itself 

 fi"om which to learn. The deposit of 

 the eg^ in ita proper place may have 

 been but the second voluntai-y act of its 

 imago life, regarding that of flight for 

 the purpose as the fii-st. Perhaps a 



