148 PROCEEDINGS OF THIRTY-THIRD FRUIT-GROWERS 1 CONVENTION. 



the planting of large areas of orchards, vineyards, grain fields, and so 

 forth, or by the importation of pests from other countries. We thus 

 find a complete disarrangement of the natural order, which generally 

 ends in great loss and damage to our industries. 



We are told that the losses caused by insect attacks on agricultural 

 products exceed the entire expenditures of our national government, 

 and that the value of these products, despite this fact, amounts to 

 about five billions of dollars, the average loss caused by insects being 

 estimated at five hundred million dollars. To all this must be added 

 the annual expenditure employed in fighting insect pests by artificial 

 means to enable us to save a portion of the crop. Huge as is this 

 annual loss, it would undoubtedly be much greater if the pests were 

 left unchecked. A great portion of the successful saving of crops 

 can be attributed to the strides made in applied entomology within 

 the last half century, including in this branch the ever-growing experi- 

 ment in insect parasitism. 



Insect parasitism has been known for a long time. Many a col- 

 lector of butterflies has been greatly disappointed, after patiently 

 waiting to rear some rare moth from his breeding cage, only to find 

 a collection of small parasites clinging to the sides of the cage, while 

 all that remained for him was the empty chrysalis with a few exit-holes 

 from which had escaped the hiding foe. 



It is within the last twenty years that insect parasitism has been 

 taken up as an economic adjunct to agriculture. The outbreak of 

 Icerya purchasi, the cottony cushion scale, in California, and the 

 knowledge of the existence of its natural enemies in its native land, 

 Australia, started one of the most interesting and most successful 

 experiments of insect control by insect parasitism ever recorded in 

 the world. No fruit-grower of California who had any interest in 

 horticulture, in the days of the Icerya plague, need be reminded of 

 the anxiety which then prevailed all over the State lest the terrible 

 white scale should forever destroy our beautiful orange groves. 



This is an instance where natural conditions had been changed by 

 man. A prolific insect had been brought by a fancier into this country 

 on some plant from a foreign country, where it had been kept in control 

 by its natural enemies; but, unfortunately, these were left behind. 

 The pest, not being checked, multiplied rapidly, and soon a great 

 struggle began between it and plant life and great loss and expense were 

 the result. To restore the balance of nature we had to introduce the 

 enemy from its natural home; and under conditions as favorable as 

 in its native land, we soon succeeded in establishing a check so com- 

 plete that now we find the pest at rare intervals and in small colonies, 

 invariably followed up by' its ever persistent enemy, Vedalia cardinalis. 



This remarkable epoch-making experiment in economic entomology 



