HEMIPTERA. 1 19 



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 Myzoxyle 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 following 

 means for preserving the apple-tree 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 mil 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 Trembley was publishing his admirable 

 researches on the freshwater Hydra, whose wonderful vitality we have 

 mentioned in our work on Zoophytes and Molluscs,* that another 

 naturalist astonished the learned world by his experiments on the 

 reproductions of plant lice. This naturalist, whose name will live 

 quite as long as those of Reaumur and of Trembley, was Charles 

 Bonnet, of Geneva. 



Charles Bonnet made the extraordinary discovery that aphides 

 can increase and multiply without the intervention of the sexes. An 

 isolated specimen can produce a series of generations of its kind. 

 We will relate the curious experiments of the Genevese naturalist. 

 He placed in a flower-pot, filled with mould, a phial full of water, 

 and put into this phial a little branch of spindle, having only five or 

 six leaves, and perfectly free from any insect. On one of these 

 leaves he placed a plant-louse, which was born under his own eyes, 

 of a wingless mother. He then covered the branch with a glass 

 shade, whose rim fitted exactly into the top of the flower-pot. Having 

 taken these precautions, Charles Bonnet was perfectly certain of being 

 able to observe his prisoner at his ease. He could keep it under his 



* "The Ocean World." 



