August, '19] SEVERIN: BEET LEAFHOPPER 319 



Stink Weed Chowchilla July 14 Aug. 18 



(Wislizenia refracta) 



Spanish Clover Manteca, beet field July 11 Aug. 15 



(Lotus americanus) 



Red Stem Filaree 4 miles west Corcoran May 20 June 25 



(Erodium cicutarium) ChowchUla May 21 June 25 



Coalinga May 22 June 27 



Cheese Weed Coalinga May 22 June 27 



(Malva parviflora) 



Alkali Mallow Connor, beet field July 18 Aug. 18 



(Sida hederacea) 



Chinese Pusley Manteca, beet field July 11 Aug. 15 



(HeUotropium curassavicum) Connor, beet field July 18 Aug. 18 



Manteca, beet field Sept. 5 Oct. 22 



Tolguacha, Jimson Weed Manteca, beet field July 11 Aug. 16 



(Datura meteloides) Le Grand, beet field July 13 Aug. 15 



Coalinga July 16 Aug. 10 



7 miles southeast Manteca . . Sept. 6 Oct. 18 



May Weed Coalinga May 22 June 27 



(Anthemis cotula) 



Common Spikeweed Chowchilla July 14 Aug. 27 



(Centromadia pungens) 



Common Sunflower Manteca, beet field July 11 Aug. 16 



(Hehanthus annuus) Le Grand, beet field July 13 Aug. 15 



Spiny Clothbur Manteca, beet field Aug. 12 Oct. 3 



(Xanthium spinosum) Manteca, beet field Sept. 5 Oct. 23 



7 miles southeast Manteca . . Sept. 6 Oct. 18 



Horseweed Chowchilla July 14 Aug. 26 



(Erigeron canadensis) 



Return Flight from Cultivated to Natural Breeding Area 



As the food plants of E. tenella become dry in the cultivated area, 

 the adults leave the vegetation. Our earliest record of the disappear- 

 ance of enormous numbers of beet leafhoppers from the Fog Weed 

 occurred between September 25 and October 10. The Fog Weed was 

 growing in an alkali sink near Cholame, situated in a mountain pass 

 between the San Joaquin and Salinas Valleys. The basin covered 

 about ten square miles and was surrounded by mountains. No speci- 

 mens were collected on green vegetation growing in and on the out- 

 skirts of the sink on Octoger 10. The two cotyledons of Filaree were 

 just appearing above the surface of the soil in the washes of the foot- 

 hills but no bugs were taken. If the leafhoppers left Cholame ^'alley, 

 then the insects either flew over the mountains or followed the passes. 



During the summer, trips were taken to the vicinity of Oro Loma, 

 where enormous numbers of leafhoppers were present on about 50 

 square miles of Russian Thistles interspersed with patches of Fog 

 Weeds. During the last week in October, the bugs were still abundant 

 on green Fog Weeds and on small Russian Thistles with the tops of the 

 plants dry and the lower portions green. An unusually large number 

 of insects had congregated on the Australian Saltbush growing along 

 the roadsides. The hoppers were common on Filaree growing below 



