50 APPLE LEAVES, PLANT-LOUSE — ITS HISTORY. 



the tree having its peeuliar species. Thus upon -the apple trge, 

 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, (JEriosoma lanigera,) which in- 

 fests the trunk and limbs, We come now to consider this, spe- 

 cies, which affects the youijg succulent ends of the twigs and the 

 haves, and an9ther species which we haye observed upon the 

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

 bably 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 was the same insect which 

 similarly infests the orchards of Europe, named Aphis Mali by 

 Fabricius; that species being described by him, by KoHar 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 European 

 ihsect, froni my esteemed friend Dr. Signoret, of Paris, and also 

 on comparing our Aphis with the description given of the Euro- 

 pean 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,) 

 pot the slightest doubt remains in my mind, but that the insects 

 of the two continents are idehtical, and that upon this side of the 

 Atlantic it has been introduced by the trees brought hither from 

 Europe. 



The his,t,ory 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 he seen numbers of small, oval, black, 

 shining eggs, from which these insects are produced. 'Scraping 

 oif the dead bark of old trees, and co iiing 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 



