3o8 Phylloxera . [ z oe 



Thus the problem of preserving the species is divided between 

 locomotion and propagation. The first generation removes the 

 ovules containing the parents of the colony from the exhausted 

 locality, the second plants that colony. 



Now it is highly probable, in fact it is almost certain, that sur- 

 rounded by an abundance of food the Phylloxera develops no 

 winged generation. This peculiarity of the insect explains a great 

 many otherwise inexplicable phenomena in its distribution, and by 

 pointing out where in the fight against the enemy our tactics have 

 been wrong, offers to us a method by which we may establish our 

 lines of defense. 



This problem resolves itself into two indications : 



First, preventing the spread of the subterranean pest. 



.Second, preventing the spread of the winged aerial pest. 



The first indication we reach in surrounding the infested spot by 

 an area that contains no food. This result may be obtained by 

 destroying the sound vines without displacing them. The exceed- 

 ingly imperfect organs of locomotion prevent the insect from travel- 

 ing a distance of, let us say, a foot. As on this way the Phylloxera 

 has to follow the more or less serpentine direction of a root, the 

 distance to be traveled to a new pasture increases. Now it is true 

 the fasting ability of this animal is considerable, but with its defect- 

 ive facilities of locomotion it would take a year to cross a girdle of 

 two feet wide, even if the insect could live so long in another than 

 an asphyctic state and would move in one direction during all that 

 time. 



The second indication, viz: to prevent the escape of the winged 

 form, we reach by covering the infested spot by some substance im- 

 penetrable by the insect. As individuals of the winged generation 

 do not possess the faculty of prolonging existence through an as- 

 phyctic state analogous to hibernation it is much easier to be dealt 

 with than with the ordinary wingless generations, which possess un- 

 der certain circumstances not yet perfectly understood a consider- 

 able power of preserving vitality. 



Of course a vineyard of which the Phylloxera once has taken a 

 perfect hold cannot be saved by all the chemicals of the world. 

 The sooner the vines are destroyed the better it is for the neighbor- 

 ing cultivations. On the other hand, it is easy enough to stop by 

 proper methods an invasion of the pest, but this is exactly the 



