Il8 THE INSECT WORLD. 



that the head is just behind the plant-louse which precedes it. There 

 they bury their trunks in the vegetable tissue, and set to work to 

 imbibe the sap. 



Small as is the trunk of the plant-louse, yet when there are 

 thousands of those little beings fixed to the stalk or the leaves of a 

 plant, it is evident that it must suffer. And so the plant-louse is, in 

 truth, one of the most terrible enemies of our agricultural and 

 horticultural productions, and the exact list of the ravages which it 

 occasions would be indeed interminable. We will confine ourselves to 

 a few examples. For some years the lime-tree aphis has seriously 

 attacked the lime-trees of the public promenades of Paris. The 

 peach-tree plant-louse causes the blight of the leaves of that tree. It 

 is to these prolific little parasites that are due, in a great number of 

 rases, the contortions of leaves and of the young shoots of trees of 

 all sorts. 



These insatiable depredators cause sometimes a still more re- 

 markable alteration. On the leaves of elms are often seen bladders 

 round and rosy, like little apples. On opening these bladders one 

 finds that they are inhabited by a species of aphis. On the black 

 poplar galls of different kinds grow, some from the leaf stalks, and 

 others from the young stems. They are rounded, oblong, horned, 

 and twisted into a spiral. Other galls show themselves on the leaf 

 itself. They are all inhabited by plant-lice, differing from those of 

 which we have given a description above, in the extremity of their 

 abdomen not presenting the two remarkable horns to which we shall 

 have later to call the attention of the reader. The body is generally 

 covered with a long and thick down. 



Of this genus, the species, alas ! so unfortunately celebrated is 

 the Apple-tree Aphis (Myzoxyle mali\ which attacks that tree. This 

 insect is of a dark russet brown, with the upper part of the abdomen 

 covered with very long white down. Its presence was announced for 

 the first time in England in 1789, and in France, in the department 

 of the Cotes du Nord, in 1812. In 1818 it was found in Paris, in the 

 garden of the Ecole de Pharmacie. It had become common in 1822 

 in the departments of the Seine, the Somme, and the Aisne. In 1827 

 its presence in Belgium was announced. 



The apple-tree aphis, according to M. Blot, can only exist on that 

 tree. Carried away and placed on any other, it very soon perishes. 

 It does not attack the blossom, the fruit, nor the leaves, but fixes 

 itself on the lower part of the trunk, whence it propagates itself down- 

 wards as far as the roots, underneath the graftings, &c. It also likes 

 to lodge in cracks of the trunk and large branches. But it always 



