December, '22] severin and basinger: beet leaehopper 419 



amount of heat received by a slope with the most favorable gradient is 

 1.4 times as great as that received by an equal area of land other con- 

 ditions being constant." The cold winds and fogs from Monterey 

 Bay sweep up the Salinas Valley but on hot days the ocean breeze 

 is very marked on the simimit of the interior hills of Little Panoche 

 Valley. No weather btu"eau records are available as to the precipitation 

 in the Panoche Hills but at Mendota near the valley trough the average 

 rainfall is 6.29 inches; the total amount for the driest year (1897) was 

 3.79 inches and for the wettest year (1906) was 10.48 inches. The 

 character of the days from sunrise to sunset during the spring is different 

 from the northren part of the San Joaquin Valley, there being fewer 

 cloudy or part cloudy days. The middle portion of the San Joaquin 

 Valley has a higher percentage of sunshine than the northern section 

 of the valley. No further discussion is necessary with reference to the 

 foothill pasture vegetation. It is evident that the vegetation, rainfall, 

 humidity of the air, cloudiness, temperature and possibly other factors 

 may play an important role as to the relative abundance of the beet 

 leafhopper in certain parts of a natural breeding area. 



Is there any danger of the beet leafhopper becoming a serious pest in 

 the future in localities where the favorable host plants are absent or do 

 not occur abundantly? As more alkali lands are placed under cultiva- 

 tion in the arid and semi-arid regions, and the alkali salts are brought to 

 the surface, the Atriplexes and other alkali loving plants will increase, 

 offering opportunities for enormous multiplication of the insect. The 

 Red Stem Filaree may spread to the foothills in localities of the western 

 states where it does not occur, furnishing a favorable host plant for the 

 first brood. Although this migratory leafhopper may encounter favor- 

 able host plants, nevertheless, climatic barriers may prevent the es- 

 tablishment of the pest. 



V. Bibliography 



1. Hall, H. M., 1902. A Botanical Survey of San Jacinto Mountains. Univ. 

 Cal. Publ. Botany, I, pp. 1-140. 



2. Hall, H. M., and Grinnell, J., 1919. Life-Zone Indicators in California. 

 Proc. Cal. Acad. Sci., IX, No. 2, pp. 37-67. 



3. Kelly, W. P., 1920. The Present Status of Alkali. Cal. Agr. Exp. Sta., 

 Cir. 219, pp. 1-10. 



4. Severin, H. H. P., 1919. The Beet Leafhopper; A Report on Investigations 

 into its Occurence in California. Facts About Sugar, VIII, No. 7, pp. 130-131, 134; 

 VIII, No. 8, pp. 150-151; VIII, No. 9, pp. 170-171, 173; VIII, No. 10, pp. 190-191; 

 VIII, No. 11, pp. 210-211; VIII, No. 12, pp. 230-231; VIII, No. 13, pp. 250, 255. 



5. Severin, H. H. P., 1919. Investigations of the Beet Leafhopper {Eutettix 

 tenella Baker) in California. Jour. Econ. Ent. XII, No. 4, pp. 312-326. 



6. Thornber, J. J., 1906. Alfilaria, Erodium cicutarium, as a Forage Plant in 

 Arizona. Arizona Agr. Exp. Sta., Bui. 52, pp. 25-58. 



