Masterpieces of Science 



they sucked its sap through their minute beaks 

 until the plant became so feeble that the 

 leaves and young fruit dropped off, a hideous 

 black smut-fungus crept over the young twigs, 

 and the weakened tree gradually died. 



In this way orchard after orchard of oranges, 

 worth a thousand dollars or more an acre , was 

 utterly destroyed; the best fruit-growing sec- 

 tions of the State were invaded, and ruin stared 

 many a fruit-grower in the face. This spread 

 of the pest was gradual, extending through a 

 series of years, and not until 1886 did it become 

 so serious a matter as to attract national at- 

 tention. 



In this year an investigation was begun by 

 the late Professor C. V. Riley, the Government 

 entomologist then connected with the Depart- 

 ment of Agriculture at Washington. He sent 

 two agents to California, both of whom im- 

 mediately began to study the problem of reme- 

 dies. In 1S87 he visited California himself, 

 and during that year published an elaborate 

 report giving the results of the work up to that 

 point. The complete life-history of the insect 

 had been worked out, and a number of washes 

 had been discovered which could be applied 

 to the trees in the form of a spray, and which 

 would kill a large proportion of the pests at a 

 comparatively small expense. But it was soon 

 found that the average fruit-grower would not 

 take the trouble to spray his trees, largely from 

 the fact that he had experimented for some 

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