16 



THE HOP APHIS IN THE PACIFIC REGIOJST. 



From these experiments, which were conducted with individual 

 insects, it was found that a period of from 8 to 12 days is required 

 for the aphides to pass through the four molts and begin depositing 

 young. 



NUMBER OF YOUNG DEPOSITED BY VIVIPAROUS FEMALES. 



Some of the experiments that were carried on to determine the 

 number of young that are deposited by individual aphides are 

 recorded in Table III. 



Table III. — Number of young deposited by each of 12 individuals of the hop aphis. 



Date. 



Number of young deposited by — 



No. 1. 



No 2.. 



No. 3. 



No. 4. No. 5. No. 6. 



| 



No. 7. 



1 

 No. 8. No. 9. 



No. 10. 



No. 11. 



No. 12. 



June 12 



4 

 5 

 7 

 4 

 7 

 2 

 4 

 2 

 

 3 

 4 

 

 3 

 5 

 3 

 3 

 5 

 4 

 1 

 2 

 

 

 









I 









13 











i 









14 



4 

 3 

 2 

 3 

 3 

 4 

 4 

 2 

 8 

 3 

 3 

 3 

 4 

 4 

 9 

 3 

 5 

 2 

 3 

 2 

 3 



1 



3 

 3 

 4 

 5 

 3 

 5 

 4 

 3 

 3 

 2 

 2 

 5 











i 









15 











i 









1G 











i 









17 

















18 

















19 

















20 



1 

 1 

 3 

 4 

 2 

 5 

 4 

 3 

 6 

 5 

 2 

 6 

 3 

 3 

 3 

 2 



. ..! 















21 



1 2 

















22 



3 

 3 

 4 

 3 



7 

 5 

 2 

 8 

 2 

 1 

 5 

 3 

 3 

 6 



2 

 3 

 2 

 8 

 3 

 3 

 3 

 2 

 3 

 5 

 2 

 6 

 4 

 

 6 

 7 

 2 

 3 

 2 

 2 

 5 

 2 

 4 

 3 

 2 

 1 



2 

 2 

 2 

 4 

 6 

 5 

 5 

 8 

 4 

 4 

 6 

 5 

 4 

 4 

 2 

 3 

 4 



2 

 3 

 2 

 3 

 9 

 4 

 7 

 6 

 

 7 

 1 

 2 

 3 

 3 

 6 

 4 

 2 

 5 

 1 

 1 

 2 



2 

 4 

 

 4 

 4 

 4 

 7 

 5 

 5 

 G 

 5 

 4 

 6 

 3 

 9 

 7 

 5 

 1 

 3 

 1 

 2 









23 









24 









25 









26 









27 



1 

 4 

 2 

 1 

 3 

 2 

 4 

 2 

 4 

 4 

 3 

 1 

 4 

 1 

 1 

 1 







28 



29 



30 



Julv 1 



2 



3 



4 



5 



2 

 4 

 1 

 8 

 3 

 2 

 2 

 4 

 

 1 

 1 

 

 1 



3 



1 

 7 

 5 

 4 

 6 

 6 

 5 



G 









6 

 4 

 1 

 3 

 G 

 5 

 4 

 2 

 2 

 3 



4 



7 









3 



8 









1 



9 









1 



10 













12 









2 



13 









2 



14 









1 



15 











i 









1G 



" 

















17 











:::.:::::::: 









18 



1 







i 











i 















Total 



08 



77 



43 



53 1 92 



87 



70 



73 



87 



38 



29 



51 











In order to obtain the foregoing data nearly mature aphides were 

 isolated on hop leaves in tin-covered jelly glasses. The leaves were 

 changed daily and the aphides which had been deposited were 

 removed. The number of young which are deposited by one stem- 

 mother were thus found to be from 29 to 92, with an average of 64 

 for the 12 aphides under observation. The length of life of these 

 aphides varied from 25 to 38 days, with an average of 30.75 days. 

 Thus an aphis living an average life of 30.75 days, depositing an 



