72 



broken on the bark after the eggs hatch out, but is generall}^ either 

 more or less mutilated or entirely removed by the weather. The 

 empty egg-shells are white, as in the other species. 



5th. The empty scales, which are supposed by Harris to have 

 produced males, may be found in considerable numbers in the autumn 

 loosely attached to the bark or some of them scarcely attached at all. 

 Towards the spring they are generally most of them washed off by the 

 weather. As these never occur on trees infested exclusively by the Oys- 

 ter-shell species, they cannot belong to that species; and I therefore, by 

 the method of exhaustion, infer them to belong to Harris's Bark-louse. 

 They are oblong-oval in shape, of a pure white color, with the usual 

 yellowish "larval scale" attached at one end, the remaining portion 

 having its sides perfectly parallel, and being as wide as the "larval 

 scale" is long, and in length from 2 to 2i times as long as the "larval 

 scale." There is no "medial scale," behind the "larval scale,'' as there 

 always is in the matured female scale of every species of this genus 

 known to me. I have never actually bred the males from this type of 

 scale, neither, as it seems, did Harris; but I have now little doubt that 

 Harris's opinion is the correct one, and that I was entirely mistaken 

 when I formerly imagined, that these empty scales were the cast skins 

 of the immature females. {Practical Entomologist, II, p. 32.) 



As to the geographical distribution of Harris's Bark-louse, Harris 

 found it, but apparently only in small numbers, in Massachusetts. 

 Dr. Houghton is pestered with it awfully in Pennsylvania, and Dr. 

 A. Chandler, Montgomery Co., Maryland, must also have it in abun- 

 dance; for he says that his pear-trees "have stopped growing and are 

 covered with white lice, which when mashed with the point of a knife, 

 discharge a i-ed fluid." {Nevj York Sem. Tribune, March 26, 1867.) 

 I have myself seen specimens near Cobden, South Illinois, some of 

 which occurred on the European Mountain Ash {Soj-bus aucuparia.) 

 a tree which Dr. Asa Gray places in the same genus as the Pear and 

 the Apple. I have likewise received specimens from the orchard of 

 W. C. Flagg, near Alton, in South Illinois. And it must occur in 

 St. Clair Co., also, in South Illinois; for at a Meeting of the Alton 

 Horticultural Society, May 2, 1867, President Pearson reported that 

 he had found "upon trees purchased in St. Clair Coimty, Bark-lice or 

 Scale-insects containing cggs,whieh when broken gave out a red-colored 

 juice." Dr. Mygatt mentions it, under the appellation of the "white 

 variety" of the Oyster-shell species, as common in Kane and McHenry 

 Counties in North Illinois, and I have long found it pretty abundantly 

 in Rock Island County, both on apple-trees and on the crab. Lastly 

 Bark-lice, which, as it would seem, can only belong to this species, are 

 reported from Hartville, Wright Co., ]\Iissouri, which is nearly in the 



