324 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



plants harbor the disease; on the one hand, the table beets, mangel 

 wurzel or stock beets, sugar beets, swiss chard or sea kale beets and 

 the weeds listed in Table III, growing in the cultivated territory and 

 on the other hand, Red Stem Filaree and possibly Bur Clover in the 

 natural breeding area. Those adults that fed on blighted varieties of 

 beets and weeds which harbor the disease in the cultivated districts 

 transmitted the disease to Filaree after their return flight to the natural 

 breeding area and those nymphs which have already hatched from 

 eggs deposited in this Filaree became virulent. After the invasion 

 of the pale green adults of the spring brood into the cultivated sections 

 the disease is again transmitted to different varieties of beets and such 

 weeds as can harbor the disease. The disease wo aid then be carried 

 over during late spring, summer and early autumn (April to October) 

 in plants growing in the cultivated regions and in late autumn, winter 

 and early spring (November to April) in plants growing on the plains 

 and foothills. 



VII. Life History 



A brief account of the life history of E. tenella under Berkeley condi- 

 tions will be given. The egg period was determined during each month 

 from February to September and varied from 16-38 days under field 

 conditions. In one experiment dark adults obtained from King City 

 were kept in a cage over winter at Berkeley. The first nymphs hatched 

 on April 15. The first adult was bred on May 15, requiring 30 days 

 to complete the nymphal instars. Twenty-two adults were reared 

 between May 15-June 27. On September 10, the nymphs of the 

 second brood began to hatch, the adults having died previous to this 

 date. The first and only adult of the second brood was found in the 

 cage on October 21. 



In another experiment 12 adults of the first generation were reared 

 on June 17-July 4, from eggs deposited on March 14. The adults of 

 the second brood were bred on November 5-15. 



An interesting observation worthy of mention, is the fact that of 

 several thousand beet leafhoppers which were reared out-of-doors at 

 Berkeley, not a single pale green or cream colored adult was bred, 

 every specimen without exception being dark. 



Dark and Light Colored Adults 



The first dark beet leafhoppers of the winter brood were captured 

 in a beet field at Manteca on September 1. When the dark forms first 

 make their appearance in the cultivated regions it is often difficult to 

 detect dark males but in the natural breeding area these are easily 

 identified during the winter. Dark females can be determined with 



