28 OTSTEE-SHELL BAllK-LOUSE. 



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tribnted. Actual observation shows that these insects, small as 

 they are, are decidedly heavier than the atmosphere, and that 

 their tendency is to fall to the ground, at no great distance from 

 the tree. That they are carried by the wind to great distances, 

 under any ordinary circumstances, is extremely improbable. To 

 produce this result we must assume the coincidence of a violent 

 gale or hurricane, such as would very rarely occur at any one time 

 year after year. And I repeat, lest it should be lost sight of by those 

 who are not familiar with the history of this insect, that there are 

 but three or four days in the year in which it is not immovably 

 lixed to the tree. In view of the inadequacy of ail the theories 

 thus far propounded, it must be admitted that the rapid and wide- 

 spread dissemination of the Apple-tree Bark-louse is yet involved 

 in much mystery, and that such instances as the occurrence of the 

 Bark-louse on the isolated crab tree above mentioned, remain to be 

 explained. 



The instrument by which this insect draws its nutriment from 

 the tree, is in the form of a long and extremely slender proboscis 

 or sucker, with a glossy surface and a redish tint, exactly resem- 

 bling a very fine hair. It is so delicate and fragile that it is usually 

 broken off in the act of removing the scale from the bark, and as 

 it generally parts at its juncture with the insect's body, it escaped 

 for a long time the notice of the most careful observers. Even so 

 acute an entomologist as Mr. Walsh, so late as the time of the 

 publication of his Report in December, 1867, although he pre- 

 sumed from analogy that such an organ must exist, and though it 

 had been discovered and described by European authors in the case 

 of allied species of the same family, nevertheless admits that " as 

 to any organized beak he could discover nothing of the kind." And 

 Mr. Kiley, in his first Report, published a year later, says : 

 " Though from analogy it must have a beak of some kind, it is so 

 exceedingly fine and fragile, that I have never been able to per- 

 ceive it." I had myself also examined hundreds of bark-lice 

 without detecting the proboscis, and indeed did not see it till 

 after I had discovered it in another and closely allied species, the 

 Coccus of the pine leaf. I had noticed that in raising these scales, 

 they did not always drop from the leaf, but sometimes hung flut- 

 tering from its surface, as if suspended by an invisible thread. This 

 occurred so many times that ray curiosity became excited to know 



