356 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1940 



the insect was found in new territory. The home gardener suffered 

 particularly from the depredations of the pest. 



High temperatures accompanied by drought during the active 

 season apparently constitute the most important natural factors in 

 inhibiting the insect's development. Winter mortality, or survival 

 of the beetles, is not an index to seasonal abundance, because of the 

 influence of spring weather conditions on the development of the first 

 generation. 



A parasite introduced from Mexico was successfully reared in large 

 numbers in the laboratory and liberated in 19 States, but as no re- 

 coveries were made in the field following these liberations it has been 

 concluded that this attempt at the introduction of a foreign parasite 

 was unsuccessful. A large number of other natural enemies have 

 been reported, but these exert little, if any, influence on the beetle 

 population. 



Magnesium arsenate was developed as a control for the pest, along 

 with calcium arsenate, cryolite, and sodium fluosilicate. Finally, 

 the rotenone-bearing roots, such as derris, cube, and timbo, were 

 shown to be the most effective insecticides. These materials could be 

 used effectively both in the form of a liquid spray and a powder 

 or dust. 



Although the insect remains an important pest of beans over the 

 greater part of the Eastern area, its depredations can be checked 

 by the proper application of the control measures now available. 



