122 THE INSECT WOELD. 



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 downwards 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 looks out for a southern, and 

 avoids a northern aspect. It is not active, walks very little, and 

 its dissemination from one place to another can only be explained 

 by the facility with which so small an insect can be transported 

 by the wind, its lightness being still more increased by the down 

 which covers it. 



The Myzoxylus mali renders the wood knotty, dry, hard, brittle, 

 and brings on rapidly all the symptoms which characterise old 

 age and decay in attacked trees. M. Blot recommends the fol- 

 lowing means for preserving the apple-trees from this insect : 

 Employ for the seed beds the pips of bitter apples only ; give to 

 the nursery and to the plants only as much shelter as is absolutely 

 necessary ; avoid those sites which are too low and too damp ; 

 encourage the circulation of air, and the desiccation of the soil ; 

 surround the foot of each apple-tree with a mixture of soot or of 

 tobacco and fine sand. 



As for the manner of freeing a tree once invaded by this insect, 

 the most simple plan is to rub the trunk and the branches, in 

 order to crush the insects, or to employ a brush or broom. 



We spoke above of the reproduction of the aphis, but without 

 entering into any particular details : we will now touch upon this 

 question, one of the most interesting in natural history. 



It was at the time when Reaumur was writing his immortal 

 " Histoire des Insectes," when Tremblay was publishing his ad- 

 mirable researches on the freshwater Hydra, whose prodigious 

 vitality we have mentioned in our work on Zoophytes and 

 Molluscs,* that another naturalist astonished the learned world 



* " The Ocean World." London : Chapman and Hall, 1?68. ED. 



