416 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



Dming the rainy season of 1919-1920, a comparative study of the 

 beet leafhopper was made in Ingram Canyon situated opposite the 

 northern part of the San Joaquin Valley and in Wild Cat Canyon oppo- 

 site the middle portion of the valley. In both canyons large nimibers 

 of adults had congregated on perennials during the autumn dispersion. 

 The pasture vegetation did not germinate until after the heavy rains 

 which fell on December 1-6, and the bugs then left the perennials and 

 were found on the Red Stem Filaree. A reduction in the nimiber of 

 dark overwintering forms occiu-red in both canyons between our visits 

 on January 15-16 and February 11-13. It was observed that the 

 females displayed no activity until sunset, the flights were exceedingly 

 low over the short Red Stem Filaree and the movement was from the 

 mouth toward the interior of the canyon. Few specimens were cap- 

 tured by sweeping with an insect-net, but by disturbing the Red Stem 

 Filaree with the hand the adults made several small leaps and were 

 often taken with a pipette. During the autumn flights the insects 

 were commonly attracted to the wind-shield of the automobile but in 

 the winter this behavior did not occur. A striking peculiarity was the 

 fact that only a single pale green leafhopper of the spring brood was 

 taken on the floor of Ingram Canyon on April 21. In Wild Cat Canyon 

 45 first generation adults were captured on the floor of the canyon and 

 foothills from 1 p. m., until simdown on April 19. During the past 

 two years dark overwintering forms were abundant in canyons in the 

 northern part of the San Joaquin Valley but in the spring instead of an 

 increase a marked reduction of the pale green specimens was evident. 



The winter months from December to February were warm and dry 

 but cold weather and heavy rains prevailed during March. The pre- 

 cipitation from September to February at Manteca was 3.96 inches, and 

 a total of 9.19 inches for the season. No fungus diseases developed 

 with any of the Jassids collected. 



During the winter and spring of 1920-1921, it was again found that 

 the dark overwintering adults were more abundant than the spring 

 brood in Hospital Canyon (12 miles south of Tracy) situated in the 

 northern part of the San Joaquin Valley. A comparison was made of 

 the number of first brood adults captured on the hillsides in the lower 

 and middle sections of the valley. Sweepings were made on the simny 

 slopes of Hospital Canyon at intervals of 100 feet to the summit at an 

 elevation of about 1,000 feet, and an average of two adults to 50 sweeps 

 of the insect-net were captured. The nimiber of first brood specimens 

 taken on the Panoche hillsides located in the middle portion of the 

 valley, however, varied from 4-61 in the same number of sweeps. 



