FIGHTING THE INSECTS 



that was threatening to exterminate the citrus orchards of Cali- 

 fornia. Later we will consider the whole question of the practical 

 use of insect parasites and predators, and this particular introduc- 

 tion will be mentioned. But we may well say something more 

 about it here. 



The scale-insect in question was very difficult to kill by means 

 of washes, since the female carried her eggs in a dense mass 

 covered by fluted wax, that was impermeable to nearly all liquids, 

 and treatment by hydrocyanic acid gas had not been invented. 

 Two of our agents, Albert Koebele and D. W. Coquillet, had 

 been spending their time in different experiments, searching 

 for some means of control. Riley, by correspondence, had learned 

 that the original home of the scale was probably Australia, and 

 that, although it occurred there, it did little damage. He urged 

 one of his correspondents, Mr. Frazer S. Crawford of Adelaide, 

 South Australia, to try to find out whether the scale had insect 

 enemies. Crawford succeeded in rearing a little parasitic fly, and 

 sent specimens to Washington. Then Riley wanted to go to 

 Australia to send this parasite over in large numbers. But the 

 regulations would not permit him to do so. Eventually he 

 secured permission from the Department of State to send two 

 men over under funds that had been appropriated for United 

 States representation at an exposition about to be held in Mel- 

 bourne. Koebele, a remarkable collector, was sent over to attend 

 to the parasites, and another assistant, F. M. Webster, went along 

 to prepare a report on agricultural features of the exposition. 

 This last was a quid pro quo to compensate the exposition fund 

 for its payment of Koebele's expenses. 



In the meantime Coquillet at Los Angeles had prepared an 

 orange tree, well stocked with scales and covered by a close gauze 

 tent, to receive the parasites. 



Koebele found the parasitic fly in small numbers, but he also 



[48] 



