OTSTBR-SHBLL BARK-LOUSE. 27 



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inverted umbrella under an infested apple tree, at this period, you 

 will soon see the little white crawling points upon it, being the 

 more easily detected from their contrast with the black back 

 ground. They can also be seen upon the grass or other objects 

 under the tree by examining with a lens. They will uniformly 

 be found further from the tree on the side towards which the wind 

 is blowing than on the other. I have also found them thickly 

 sprinkled upon the upper surface of cob-webs which happened to 

 be spread over the grass at the distance of two or three rods from 

 the tree. ,^ Being caught on the web, it was evident they could not 

 have crawled there, but that they must have fallen there from 

 above. 



An interesting query here suggested itself as to the degree of 

 tenacity with which these insects adhere to the tree at this period, 

 and how strong a wind it requires to remove them. To deter- 

 mine .this point Ij experimented by blowing upon them with my 

 mouth, with diflterent^degrees of intensity. I found that a pretty 

 strong current of wind did not disturb them, provided it was 

 steady and uniform, but that a short, sharp puff readily dislodged 

 them. At one time, during my examination, the wind arose and 

 blew a pretty stiif breeze, and I could feel it sweep over the sur- 

 face I was examining with considerable force ; yet in only a very 

 few instances could I perceive that any of the Coccids were blown 

 oiF; and yet actual observation showed that the ground beneath 

 was thickly sprinkled with thera. The query arises whether these 

 creatures may not have an instinct to loosen their hold upon the 

 tree, irrespective of the force of the wind, for the purpose of dis- 

 semination. This may seem improbable, but it is no more won- 

 derful than many of the instincts of insects. 



A still more important question is, how far they can be trans- 

 ported by the wind. This will depend very much, of course, upon 

 the force with which the wind may happen to be blowing, at any 

 given locality, at the hatching period. At the time I made part 

 of my observationB, last spring, there was a pretty fresh breeze 

 blowing, but I did not detect any Coccids upon the ground beyond 

 about three rods from the extreme branches of the trees. Never- 

 theless, some of them may have been carried farther, for it must 

 be borne in mind that it is not an easy thing to find such minute 

 objects upon the ground, except where they are numerously dis- 



