FIGHTING THE INSECTS 



are hatched against the United States Treasury than in any other 

 one place." 



The thirteen years o£ 1881 to 1894, filHng the time between 

 Comstock's departure and Riley's resignation as Chief of the 

 Service, must not be dismissed summarily, since it was a time 

 of achievement as well as of development and education. In the 

 last chapter I have mentioned what was perhaps the crowning 

 achievement of Riley's second regime, namely the introduction 

 of the Australian Ladybird, which really started the important 

 line of natural control work. But there were other rather big 

 things. 



A notable one, now almost forgotten, was the solving of the 

 problem of the hop plant-louse. Although it was only one of 

 several important studies, it had interesting and unique features. 

 This was long before the sad days of Prohibition. The beer- 

 manufacturing industry was very important. Hops were grown 

 extensively in many regions, although the landscape was not 

 dotted with hop yards as, for example, are certain regions in 

 Kent and in the country south of Budapest. The largest centers 

 of hop production in the States were probably in portions of 

 New York, Wisconsin and Washington. It had been known in 

 England that the worst insect pest of the hop crop, namely the 

 hop plant-louse, occurred both on the hop and on the plum. 

 But its rather extraordinary life history had not been worked out. 

 Riley started an investigation which was successfully carried on 

 by his assistants to a rather brilliant conclusion. The field work 

 was done at Richfield Springs, New York, practically wholly by 

 Theodor Pergande, who spent the better part of 1886 at that 

 point. Professor Riley was in Europe at the time, and I visited 

 the field in the summer of 1886 to check up Pergande's observa- 

 tions. W. B. AUwood was there, engaged largely on the subject 



