December, ’23] severin: investigations of beet leafhopper 
481 
migration of the beet leafhopper occurs from the San Joaquin Valley 
into the Salinas Valley through the Coalinga-King City mountain pass. 
There was no evidence to show that an enormous congregation of the 
insects occurs on the east side of this mountain pass during the spring. 
Wherever annual saltbushes grow in the mountain passes along road¬ 
sides, or covering alkali sinks, leaf hoppers may be taken, which con¬ 
gregated on these plants after the pasture vegetation became dry on 
the foothills. The general distribution of the hoppers on annual Atri- 
plexes in the mountain passes indicates that these insects have a keen 
sense of smell. Those leaf hoppers which assemble on favorable food 
and breeding plants during the spring flights remain in the cultivated 
foothill regions together with the later summer generations. 
During the period 1918-1921, the first appearance of the pale green 
spring brood adults in the cultivated areas of the Salinas and San 
Joaquin Valley occurred as follows: 
Salinas Valley San Joaquin Valley 
1918 May 8, King City 1918 April 24, upper. 
1919 April 22, King City 1919 April 8, 14, 28, upper, middle, lower. 
1920 April 22 or 23, King City 1920 April 23, upper. 
1921 April 25 to 30, King City 1921 April 6, 14, upper, middle. 
V. Autumn Dispersal 
During 1918, the first indication of an autumn dispersal of the dark 
overwintering adults occurred on October 11 to 13, in a mountain pass at 
Bitterwater about 15 miles northeast of King City. The insects had 
left the dried Redscale or Red Orache but some of the hoppers were still 
present on partly green Silver scale or Fog Weed growing in a large alkali 
sink. A congregation of adults had occurred on green pasture vege¬ 
tation growing at the base of the foothills adjacent to the alkali sink. 
The movement of the dark overwintering adults from the alkali sink 
was not toward the San Joaquin Valley but in the opposite direction. 
During the autumn dispersal in the Salinas Valley the dark over¬ 
wintering adults were rarely taken on Red Stem Filaree (Erodium 
cicutarium )growing on the foothills within the fog belt. The leafhoppers, 
however, were captured more abundantly outside of the fog belt be¬ 
tween Greenfield and King City and were far more numerous on the 
northeastern than on the southwestern foothills of the Gabilan and 
Sierra Santa Lucia ranges respectively. 
During the autumn of 1919, large numbers of dark overwintering 
adults disappeared from the experimental field at King City on Novem¬ 
ber 21. After the beets are topped large numbers of nymphs probably 
succumb in a dry autumn unless they are able to obtain food from 
