FIGHTING THE INSECTS 



and many other portions of the world. It is known in other 

 countries as "The American Bhght." In most parts o£ America, 

 especially where the soil is light or rather sandy, this pest lives 

 principally upon roots; but in England and France, especially in 

 clayey soils, it multiplies enormously aboveground and seriously 

 drains the vitality of the trees. 



When in the United States this insect appears aboveground 

 on suckers from the trunk, it is destroyed by many other insects, 

 but particularly by a very minute parasite known as Aphelinus 

 malt. 



Dr. Paul Marchal had talked to me about the advisability of 

 importing this parasite into France, but soon after that the war 

 came on and all else was forgotten. When peace came, and re- 

 habilitation on a large scale began in France, Marchal's functions 

 were enlarged, and he was given more assistants, which enabled 

 him to establish several field laboratories. Then he was ready 

 to attempt the introduction of the Aphelinus. We were only too 

 glad to have a chance to help him, for we owed him much. So 

 in the spring of 1920 I had men in several different parts of 

 the United States gather twigs of apple and pear, the twigs 

 selected being, for the most part, suckers bearing the dead and 

 swollen bodies of the plant-lice. Each of these swollen bodies 

 contained a dormant parasite. These twigs were carefully packed 

 in small boxes, and the boxes themselves were made into a 

 packet a foot or so square. In late May I started out with this 

 packet in my luggage. While at Washington it had been kept 

 at a temperature of about forty degrees F. Arriving in New 

 York, I boarded the boat and at once consulted the Chief 

 Steward, By his orders, the man in charge of the meats placed the 

 packet upon a shelf in his refrigerating room, the temperature 

 of which I was assured ran from 37° to 41° F. Each day of the 

 journey the temperature of this room was reported to me, and 



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