AUTHOR'S PREFACE 



CE radical changes in conditions during the 

 past eight or ten years along agricultural and 

 commercial lines have been followed by the 

 general distribution of many insect pests of a 

 serious character. In commercial transactions the dan- 

 gers have been so great along certain lines that many 

 State laws have been enacted to prohibit the distribu- 

 tion of such insects as the San Jose scale and others of 

 a dangerous nature. Some foreign governments have 

 enacted such legislation as to make it practically im- 

 possible to ship fruit and nursery stock without the 

 most rigid inspection and fumigation before entry is 

 permitted. 



Ability to successfully combat noxious insects is a 

 problem of the most vital importance to farmers, fruit 

 growers, nurserymen, gardeners, florists, millers, grain 

 dealers, transportation companies, merchants, grocers, 

 housekeepers and others. This is especially true of 

 the fruit, nursery, and grain industries. The use of 

 hydrocyanic acid gas and carbon bisulphid, two very 

 powerful insecticides, have largely solved these serious 

 problems. We owe the discovery of carbon bisulphid 

 as an insecticide to M. Doyere, while that of hydrocyanic 

 acid gas belongs to D. W. Coquillett. Their practical 

 application has been one of gradual development. 



With the advent of the San Jose scale in Eastern 



