412 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



Investigations have been conducted in the San Joaquin Valley during 

 the past four years and the factors associated with the natural breeding 

 grounds of the leafhopper will be discussed in this paper. 



II. Favorable Breeding Plants of Beet Leafhopper in 

 Cultivated Area 



The most noticeable feature in regard to one condition which is 

 favorable for an enormous increase of the leafhopper in the San Joaquin 

 Valley, is the abundance of the host plants upon which this insect feeds 

 and deposits its eggs in the cultivated area. In 1919, we (4) published 

 a paper showing the relative number of beet leafhoppers captured on 

 plants growing in the cultivated area of the San Joaquin Valley and 

 also a list of plants in which eggs were deposited. The plants upon 

 which enormous numbers of nymphs and adults were taken are repre- 

 sentatives of the Saltbush Family {Chenopcdiaceae) to which the sugar 

 beet belongs. The hopper was bred from eggs deposited in 35 species 

 of plants growing under natural conditions in the cultivated area. 

 Later investigations showed, however, that although the females may 

 deposit eggs in certain plants, the nymphs are not able to acquire the 

 winged stage by feeding on these plants. Our breeding experiments 

 also indicate that the most favorable host plants in the cultivated area 

 are the representatives of the Chenopodiaceae and closely related families. 



Wherever man has injuriously disturbed the natural conditions in the 

 San Joaquin Valley, vast areas of annual saltbushes {Atriplexes) occur. 

 These plants, which grow on alkali soil, are commonly found along 

 roadsides and highways. Dense masses of these plants occur along 

 fences. During the autumn and winter, the stalks of the larger species 

 break off near the soil and are rolled along the groimd by the wind 

 scattering the seeds. The weeds pile up along barb-wire fences dropping 

 their seeds and this probably explains why certain species of Atriplex 

 are so common along fences. Miles and miles of saltbushes grow along 

 railroad tracks. Vacant fields are often covered with thick growths of 

 these alkali plants. Alkali sinks are surraunded by dense masses of 

 this vegetation but often the black alkali is too strong for their develop- 

 ment. After the grain is harvested, the stubble fields become covered 

 with Atriplex. Hay and straw stacks are commonly surrounded by 

 saltbushes. Irrigation and drainage canals are favorable locations 

 for the development of this alkali vegetation. 



What has been the stimulus for the development of enormous areas 

 of annual saltbushes in the San Joaquin Valley? According to Kelly 

 (3) "several hundred thousand acres in the San Joaquin Valley, which 

 were comparatively free from alkali previous to the advent of irrigation, 



