282 FIELD, FOREST AND FARM 



scars, shrivel up and can grow no larger. For this 

 ill there is no remedy; the harvest is ruined. 



"The gardener pulls it all up and throws it on the 

 dung-hill. His care and vigilance have been unable 

 to arrest the invasion. In vain he crushed legions at 

 a time under his angry heel : in a few days the half- 

 dozen survivors had propagated a larger colony 

 than ever. Man is hardly in a position to contend 

 successfully against this lowly vermin which braves 

 extinction by virtue of its countless numbers. 

 . "As I told you, the plant-louse does not like to 

 change its place. It plants its sucker on the very 

 spot where it has just been born, and thenceforth 

 sticks to that spot, filling its stomach with sap and 

 surrounding itself with a family. This love of re- 

 pose explains to us very well how the twig of a rose- 

 bush or the top of a beanstalk undergoes a progres- 

 sive colonization ; but it does not account for the dis- 

 tant propagation of the species. 



"With its home-keeping habits the insect ought 

 to be confined within narrow limits, on a single leaf 

 and not on all leaves, on one rosebush and not on 

 the neighboring rosebushes. But as a matter of fact 

 it is disseminated everywhere. When one patch 

 of beans becomes infested, those in the neighborhood 

 are equally unfortunate; when one rosebush shows 

 a colony of plant-lice, all those around it are simi- 

 larly visited. No vegetable growth can defend it- 

 self from the pest. How, then, is it that this obese 

 animalcule, which totters with fatigue after one step 

 forward, succeeds in passing from rosebush to rose- 



