12 



established whether it is hereditary or not. There is at present 

 no argument that can be brought against the heredity of the 

 disease, while there are some important facts which indicate its 

 heredity. These will be considered later. 



II. Resume of Some Experiments with Flacherie in 1909. 



Fischer called attention, in his excellent paper, already men- 

 tioned, to the manner in which Flacherie can be artificially 

 developed. He says that the disposition to the disease is 

 secured by giving the caterpillars food which has been placed 

 in water and renewed only every three or four days. This 

 treatment apparently causes an injury to the leaf protoplasm, 

 due to the presence of too much water, and there is a con- 

 comitant increase in the acidity of the leaves. 1 If, now, a cater- 

 pillar eats such leaves, the alkalinity of its digestive fluid, 

 which is very strong in healthy individuals, decreases, and in 

 this manner the first susceptibility to the disease is given. 

 Before the visible outbreak of Flacherie, Fischer could recog- 

 nize as an early symptom a characteristic sweet odor in the 

 breeding cages, which could be compared best to that of some- 

 what withered lilac blossoms. Whenever this odor was notice- 

 able Flacherie soon made its appearance, and as it progressed 

 the odor increased proportionately. Fischer recommends the 

 artificial production of Flacherie among the caterpillars of the 

 " nun " (" die Nonne " of the Germans) by intentionally giv- 

 ing the larvae this kind of food as soon as an abundance of the. 

 pest is noted in any particular locality. 



Bearing in mind the close relationship existing between the 

 " nun " and the gypsy moth, I attempted during the summer 

 of 1909 to put Fischer's conclusions regarding the artificial 

 production of the wilt to a practical test. These experiments 

 were published in detail in the entomological journal " Psyche," 

 Vol. XVI., No. 5, October, 1909. There appeared also a Ger- 

 man translation of the paper in the " Societas Entomologica," 

 Jahrgang XXIV., pp. 178-181, Zurich, Switzerland. The 

 main facts in these experiments are here noted. Up to 70 

 per cent, of the caterpillars were killed by artificially produced 



* * See the'experiments which Sasaki performed on mulberry trees in Japan, "Zeitschrift fur 

 Pflanzenkrankheiten, " XII. Band, Jahrgang 1902, 4. Heft, pp. 203-226; 5. Heft, pp. 258-278. 



