414 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



common European weed; Nettle Leaf Goosefoot (Chenopodium murale), 

 naturalized from Europe; Mexican Tea {Chenopodium amhrosioides) , 

 naturalized from tropical America; Chenopodium leptophyllum, native. 



Another favorable host plant belonging to the Chenopodiaceae is the 

 Russian Thistle (Salsola kali tenuifolia) . This obnoxious weed is a 

 native of Asia and first appeared near Bakersfield in 1895, and is abun- 

 dant and highly pernicious in many parts of the San Joaquin Valley. 

 Enormous hordes of leafhoppers develop on this plant in the middle and 

 southern parts of the valley. 



The beet leafhopper has been bred from one other host plant (Nitro- 

 phila occidentalis) belonging to the Chenopodiaceae, and both nymphs 

 and adults are commonly found on this plant in the San Joaquin Valley. 

 It is found on moist alkali soils, often on black alkali in California, 

 Nevada and Oregon. 



A plant from which the beet leafhopper has been bred and upon which 

 large numbers of nymphs and adults are commonly taken in the field is 

 the Lowland Purslane (Sesuvium sessile) belonging to the Carpet Weed 

 Family (Aizoaceae). This plant is found on river lowlands and alkali 

 fields in the San Joaquin Valley. 



in. Favorable Breeding Plants of Beet Leafhopper on 

 Plains and Foothills 



There existed on the plains and hills of California an abundance of 

 grasses, clovers, and wild flowers, until man disturbed the natural 

 conditions. As early as 1773, the Spaniards disturbed the native con- 

 ditions by introducing sheep which carried in their wool seeds of plants 

 from the Mediterranean basin. An active competition between the 

 native and introduced plants has occurred to such an extent that most of 

 the native species have been greatly diminished. In all probability, the 

 original foothill host plants of the beet leafhopper were encroached upon 

 by the introduced plants. A special adaptation of the leafhopper to 

 Alfilaree or Red Stem Filaree {E. cicMtarium) occurred, which has spread 

 to the barren hillsides and dry plains. Cattle and sheep have over- 

 grazed the preferred introduced forage plants so that these were not 

 permitted to produce seeds abundantly. It is these over-grazed foot- 

 hills in the semi-arid regions that are the most favorable habitat of this 

 insect. The enormous area which the Red Stem Filaree now covers 

 according to Thomberg (6) in parts of Washington, Idaho and Texas, 

 and the whole of Oregon, California, Nevada, Arizona, New Mexico and 

 Utah furnished an enormous increase in the food supply of this pest, 

 compared with the original, native host plants. It was the disturbance 



