71 



and from their being very sluggish in their movements, they can 

 scarcely be seen on the bark with the naked eye. On June 12th, I 

 observed some — which I identified as belonging to this species because 

 they were still under the parent scale — to be of a pale blood-brown 

 color, without any powdery bloom; they had the same longitudinal 

 ridge and transverse grooves as the other species. The inexperienced 

 eye, if it noticed them at all at this date on the bark, would be almost 

 sure to confound them Avith the natural pores of the bark, which at 

 first sight they greatly resemble. 



2d. I have been unable to trace satisfactorily the history of 

 Harris's Bark-louse from June to September, because the Oyster- 

 shell species had invaded every one of my trees, that had been orig- 

 inally occupied exclusively by the native species; so that it was diffi- 

 cult to distinguish one kind of larva from the other kind. I could 

 only ascertain one point clearly, namely, that the matured scale of 

 the female, which is milk-white, is not formed till about the middle of 

 September, and that the eggs are not developed under that scale till the 

 end of September or some time in October; whereas, as we have seen, in 

 the other species the matured female scale, which is the color of the 

 bark, is formed, and the eggs fully developed, by the middle of August. 

 Certainly, from the middle of June to about the middle of September, 

 the females must remain of the same dark inconspicuous color as be- 

 fore; for the white scales, which are so conspicuous, appear all of a 

 sudden on the bark in the middle of September. Dr. Houghton, of 

 Philadelphia, as well as myself, noticed this fact. He has 20,000 

 pear-trees badly afflicted by this pest. "Up to September 15th," he 

 says, "I flattered myself that there was not a living insect of this 

 description in my orchard. I thought that the winter of 1865 — 6 had 

 been so cold, that it had killed them all. But lo ! on the 20th of 

 September there were millions upon millions of Bark-lice on my pear- 

 trees." (Practical Entomologist, II., p. 30.) 



3d. On September 17th, or some weeks before any eggs were de- 

 veloped, I lifted up over 10 perfected female scales. Under each of 

 them, and entirely separated from the scale itself, I found a legless, 

 beakless, fleshy, elongate-oval Bark-louse, about 2^ times as long as 

 wide, with its body divided into pretty distinct segments, the 3 first 

 of which, and in a less degree the 2 next, were very much hunched 

 laterally. The color was yellow, blood-red, or pink, and the length 

 about 0.03 inch. One of these / saw move very distinctly, showing 

 that it was really alive. 



4th. The scale of this species is of a much more delicate consist- 

 ence than that of the Imported Bark-louse, and it rarely remains un- 



