HEMIPTERA. 193 



of this kind, as big as a pigeon's egg, growing upon leaves, to 

 which they were attached by a slender neck, and containing thous- 

 ands of small lice in their interior. Naturalists call these tumors 

 galls, because they seem to be formed in the same way as the 

 oak-galls which are used in the making of ink. The lice which 

 inhabit or produce them generally differ from the others, in hav- 

 ing shorter antennae, being without honey-tubes, and in frequently 

 being clothed with a kind of white down, which, however, disap- 

 pears when the insects become winged. 



These downy plant-lice are now placed in the genus Eriosoma, 

 which means woolly body, and the most destructive species be- 

 longing to it was first described, under the name of Aphis lani- 

 gera, by Mr. Hausmann *, in the year 1801, as infesting the apple- 

 trees in Germany. It seems that it had been noticed in England 

 as early as the year 1787, and has since acquired there the name 

 of American blight, from the erroneous supposition that it had 

 been imported from this country. It was known, however, to the 

 French gardeners f for a long time previous to both of the above 

 dates, and, according to Mr. Rennieij:, is found in the orchards 

 about Harfleur, in Normandy, and is very destructive to the ap- 

 ple-trees in the department of Calvados. There is now good 

 reason to- believe that the miscalled American blight is not indi- 

 genous to this country, and that it has been introduced here with 

 fruit-trees from Europe. Some persons, indeed, have supposed 

 that it was not to be found here at all, but the late Mr. Buel has 

 stated § that it existed on his apple-trees, and 1 have once or 

 twice seen it on apple-trees in Massachusetts, where, however, it 

 still appears to be rare, and consequently I have not been able to 

 examine the insects sufficiently myself. The best account that I 

 have seen of them is contained in Knapp's " Journal of a Nat- 

 uralist", from which, and from Hausmann's description, the fol- 

 lowing observations are chiefly extracted. 



The eggs of the woolly apple-tree louse are so small as not to 

 be distinguished without a microscope, and are enveloped in a 

 cotton-like substance furnished by the body of the insect. They 



* Illiger's Magazin, Vol. I. p. 440. t Salisbury's Hints on Orchards, p. 39. 

 t Insect Miscellanies, p. 180. § New England Farmer, VII. p. 169 ; IX. p. 178. 



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