50 APPLE LEAVES, PLANT-LOUSE ITS HISTORY, 



we have already noticed the Apple root blight, a species of woolly 

 louse producing excrescences upon the roots, and the Apple Bark 

 louse. There is also the tree blight (Eriosoma lanigera), which 

 infests the trunk and limbs. We come now to consider this 

 species, which affects the young succulent ends of the twigs and 

 the leaves, and another species which we have observed upon 

 the leaves, which appears to be distinct from the Mali, though 

 probably possessing the same habits. We thus have five kinds 

 of these vermin infesting our apple trees. 



In many instances it is extremely difficult to determine whether 

 the lice upon our American trees and plants are identical with 

 those which occur upon the same or similar vegetation in Europe, 

 the descriptions given of them by the old authors being so very 

 brief, and often drawn up from a superficial examination of the 

 species. And I have heretofore been in much doubt whether this 

 common Aphis of our apple trees w r as the same insect which 

 similarly infests the orchards of Europe, named Aphis Mali by 

 Fabricius; that species being described by him, by Kollar and 

 others, as being of a green color, whereas, our insect in its winged 

 state is almost invariably black, its abdomen only being green. 

 But having recently been favored with specimens of the Euro- 

 pean insect, from my esteemed friend Dr. Signoret, of Paris, and 

 also on comparing our Aphis with the description given of the 

 European by M. Amyot, (Annals Entom. Soc. France, 2d series, 

 vol. v. page 478,) and the detailed account of the veins of its 

 wings, furnished by Mr. Walker, (List of British Museum, page 

 985,) not the slightest doubt remains in my mind, but that the 

 insects of the two continents are identical, and that upon -this 

 side of the Atlantic it has been introduced by the trees brought 

 hither from Europe. 



The history of this species and its annual career is as follows : 

 Early in the spring, sunk deep in the cracks and crevices in the 

 bark of the apple trees, may be seen numbers of small, oval, black, 

 shining eggs, from which these insects are produced. Scraping 

 off the dead bark of old trees, and coating the trunks of all the 

 trees with whitewash at that period of the year is a practice of 

 much utility, since thereby most of the eggs of this and some other 



