Nov. 15, 1920 Life History and Habits of the Beet Leaf hopper 249 



Weather conditions were severe enough during the winter in this dis- 

 trict to necessitate hibernation. All attempts to determine the method 

 of hibernation, however, as well as the places in which it takes place 

 were failures. Adults in cages survived the winter underneath dead 

 beet leaves and in the crown of the plant. 



EN CALIFORNIA 



Under California conditions adults and nymphs are most abundant 

 in the field during August. At harvest time they are scattered, and no 

 doubt a large number perish. After the beets have all been removed 

 from the fields the leafhoppers seem to be greatly diminished in numbers, 

 although they may be collected from certain weeds growing in the fields 

 and along the irrigating canals. No indications of a general migration 

 have been noted at such times, so it is assumed that the surviving individ- 

 uals scatter over wild vegetation, selecting that which is most suitable 

 for food and protection. Later they may congregate in certain spots 

 which furnish especially favorable conditions during winter. 



There is no true hibernation in the districts of California that have 

 been under observation. Adults have been collected every week in the 

 winter under conditions indicating that they were feeding when captured. 

 Under cage conditions food must be available at all times. As a rule, all 

 individuals kept without food died within 48 hours. 



The characteristic dark-colored individuals of the fall brood that leave 

 the beet fields could hardly be confused with the light-colored adults 

 that appear the next spring. A small percentage of the fall-brood 

 adults may remain in or near the beet fields during the winter and be 

 responsible for the early injury in the spring, but it is usually not until 

 the light forms appear in considerable numbers that attention is directed 

 to the damage. The striking difference in coloration between the fall 

 and spring forms suggests at once the possibility of a new brood on wild 

 vegetation before migration into the beet fields. Observations and cage 

 experiments have proved that such a brood occurs. 



The time when the leafhoppers first appear in fields in spring in Cali- 

 fornia varies with the seasonal conditions in different localities, being 

 from April 1 to June 1. The condition of wild vegetation in the natural 

 breeding areas is an important factor in determining when migration to 

 the beet field will take place. As long as this vegetation is abundant and 

 succulent it is doubtful if there is any general movement into the culti- 

 vated areas. 



Oviposition begins as soon as the adults appear in the field and con- 

 tinues throughout the season. There is an overlapping of broods 

 which makes it impossible to determine the exact number under field 

 conditions. Cage experiments, however, have demonstrated that there 

 may be from one to three each year on the beets. Thus the maximum 

 number of broods in one year would be four. 



