December, '22] severin and basinger: beet leafhopper 415 



of the native conditions on the plains and foothills and in the cultivated 

 area that has increased the most favorable food and breeding plants of the 

 leafhopper and hence has increased the opportunities for an enormous 

 multiplication of the pest when climatic conditions are favorable. 



IV. Favorable Habitat of Beet Leafhopper 



Investigations conducted on the plains, canyons and foothills after 

 the autupin flights of the beet leafhopper lead to the discovery of the 

 most favorable habitat of this insect in the San Joaquin Valley. A 

 brief account of the observations made during the rainy season of the 

 past three years will be given. 



We (4, 5) have published the results of our observations conducted 

 during 1918, on the autumn dispersion of the leafhopper and recorded 

 large numbers of the pest on the plains and foothills of the Coast Range, 

 Tehachapi foothills in the vicinity of Tejon Pass and Sierra Nevada 

 foothills four miles east of Famosa to Bakersfield. The pasture 

 vegetation germinated after the heavy rains which fell on September 

 11-13, and wherever the Red Stem Filaree was swept with an insect- 

 net the hoppers were captured during October and November. Nymphs 

 were also taken on the plains and foothills; these probably hatched 

 from eggs deposited by the stimmer brood adults which acquired the 

 winged stage during late summer or early autumn. A trip was taken on 

 December 13, to the Tehachapi mountains which were snow-capped; 

 no leafhoppers were observed on the foothills but 50 specimens were 

 caught in two hours on the plains about five miles north of the foothills. 

 During January no investigations were made but in February and 

 March, a marked reduction of the overwintering forms was observed 

 on the northern foothills and in canyons. A remarkable peculiarity 

 noted in April, was the fact that the pale green adults of the spring 

 brood were rarely captured on the foothills and in canyons in the 

 northern portion of the San Joaquin Valley. 



During December large niunbers of Jassids were collected on the 

 foothills bounding a canyon (13 miles southwest of Tracy) in the northern 

 part of the San Joaquin Valley and when these were confined in cages in 

 the greenhouse at Berkeley, they died as a result of a fungus disease. 

 The weather bureau records kept by the Spreckels Sugar Company at 

 Manteca showed that the precipitation from September to April was 

 17.29 inches; 9.98 inches of rain fell from September to December. 

 We (4, 5) have published the fact that heavy rains kill some of the leaf- 

 hoppers in the cultivated territory. 



