CANKBK-WORM. lH 



upon her back on a piece of glass, she cannot get sufficient tbot-hoid to 

 turn over, and I experimented for some time with them before I saw 

 any of them succeed in crawling up a perpendicular glass surface. But 

 1 found that they can do so, though with difficulty, and they sometimes 

 drop off in the attempt. They adhere to smooth surfaces in the same 

 way that the house-fly does, that is, by means of a little adhesive pad 

 (planiula,) situated between the claws at the extremity of the feet, 

 but with this difference, that the moth has but one pad to each foot, 

 and the fly has two, and the brush of hairs upon the under side of the 

 pad is more dense in the fly. 



In the course of my experiments I made the following observations, 

 which seem to furnish the key to a practically complete control of this 

 notorious insect. I first tried the experiment of putting round the 

 trunk of one of the infested trees a plain tin band four inches wide. 

 The result is thus recorded in my diary : 



March 13. — Went out at eight o'clock with a lantern to see how the 

 experiment worked. Mercury at Si*^. The moths were ascending m 

 considerable numbers. There was a dense crowd of moths all around 

 the tree just below the tin band. A considerable number had crawled 

 on to it, bat most of these seemed to be merely holding on without 

 much disposition to pass over it. Thoy were evidently baulked in their 

 instincts. I occasionally saw one drop to the ground. A very small 

 proportion had traveled over on to the tree above. 



March 15. — Very warm. Moths very abundant, as recorded above. 

 Tried the experiment of putting another tin band outside of the first, 

 with a piece of inch rope between them so as to close the passage. 

 The moths came up in crowds, but did not accumulate between the 

 bands as I had expected, but below the inner one, as in the former exper- 

 iment. It appears, therefore, that if a plain tin band, four inches wide, 

 be put round the trunk of a tree, the moths will congregate below it, 

 but will not freely go on to or over it. A small proportion go over, 

 and seem to do it without any great degree of difficulty. That they 

 do not more readily and more generally pass over, can only be ex- 

 plained upon the supposition that the insects are baulked or disconcer- 

 ted. They find on the polished surface none of the shelter which their 

 instincts teach them to seek for their eggs, and they are at a loss what 

 course to take. When the instinct which impels the wingless mother 

 of the Canker worms to make her way up the tree witti such untiring 

 zeal and pertinacity, was inscribed in the great book of Nature, the in- 

 tervention of a polished tin band was not in the programme. 



