320 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



the Russian Thistles. Adjacent to the western margin of this large 

 area of weeds were the plains which extended about 3 miles to the foot- 

 hills and on both, the adults were often taken on Filaree. 



It is not to be assumed that the hoppers are found only on the foot- 

 hills along the margin of the San Joaquin Valley. In crossing the 

 Coast Range through the Altamont Pass, the adults were taken on 

 Filaree growing on the foothills situated about 4 miles from the western 

 margin of the San Joaquin Valley. 



During the winter E. tenella was not found on foothills which were 

 densely covered with green vegetation but the hoppers seek those hills 

 which are sparsely covered with Filaree. As a general rule, the leaf- 

 hoppers were taken on foothills which were exposed to the sunshine 

 during the morning and afternoon. In all probability, the position of 

 one hill to another with reference to sunshine determines the choice of 

 location for the winter. 



During the last three months of the year the beet leafhoppers were 

 found on Filaree growing on the plains or foothills in the following 

 localities on the west (Coast Range), south (Tehachapi Mts.) and east 

 (Sierra Nevada Mts.) sides of the San Joaquin Valley: 



Foothills south and west of Tracy. 



Foothills 13 miles southwest of Tracy. 



Foothills 13 miles southwest of Tracy. 



Base of foothills, west of Dos Palos. 



Plains and foothills west of Oro Loma. 



Plains 7 miles north of Bakersfield. 



Plains 3-10 miles west of Lost Hills. 



Plains and foothills in the vicinity of Tejon Pass. 



Plains 21 miles south of Bakersfield. 



Plains and foothills east of Famosa to Bakersfield. 



If we correlate the facts discovered in the natural and cultivated 

 portions of the San Joaquin Valley, one would not hesitate to make the 

 following statements: After the pasture vegetation became dry on 

 the plains and foothills, the beet leafhoppers flew into the cultivated 

 districts. During the summer an occasional specimen was taken on 

 the various plants growing on the plains and foothills, showing that 

 not all of the hoppers leave their natural breeding grounds. The inva- 

 sion of the pest into the cultivated sections began on April 24, continued 

 until May 21, and probably later. The gradual disappearance of the 

 bugs in the cultivated regions during October corresponded with the 

 reappearance of the insects under natural conditions. All of the 

 adults do not leave the cultivated localities and last spring these caused 

 4 per cent of blighted beets at Manteca. Apparently no adults were 

 present in the cultivated area from April 7-22, but nymphs were found 



