10 



BULLETIN 100, U. S. DEPAETMENT OF AGRICULTURE. 



Table III.- — Life cycle of the third generation of Chromaphis juglandicola, San Jose, 



Cat., 1911. 



No. of 

 indi- 

 vidual. 



Date of— 





No. of 

 indi- 

 vidual. 



Date of— 





Depo- 



Acquir- 



Life 

 cycle. 



Depo- 



Acquir- 



Life 

 cycle. 





sition. 



wings. 







sition. 



ing, 

 wings. 











Days. 









Days. 



1 



May 19 



June 4 





50 



May 19 



June 7 



19 



2 



19 



4 





51 



19 



7 



19 



3 



19 



4 





52 



19 



7 



19 



4 



19 



4 





53 



19 



7 



19 



5 



19 



5 





54 



19 



7 



19 



6 



19 



5 





55 



19 



7 



19 



7 



19 



5 





56 



19 



7 



19 



8 



19 



5 





57 



19 



8 



20 



9 



19 



5 





58 



19 



8 



20 



10 



19 



5 





59 



19 



8 



20 



11 



19 



5 





60 



19 



8 



20 



12 



19 



5 





61 



19 



8 



20 



13 



19 



5 





62 



19 



8 



20 



14 



19 



5 





63 



19 



8 



20 



15 



19 



5 





64 



19 



8 



20 



16 



19 



5 





65 



19 



9 



21 



17 



19 



5 





66 



19 



9 



21 



18 



19 



6 





67 



22 



10 



19 



19 



19 



6 





68 



22 



11 



20 



20 



19 



6 





69 



22 



11 



20 



21 



19 



6 





70 



22 



11 



20 



22 



19 



6 





71 



22 



11 



20 



23 



19 



6 





72 



22 



11 



20 



24 



19 



6 





73 



22 



11 



20 



25 



19 



6 





74 



22 



11 



20 



26 



19 



6 





75 



22 



11 



20 



27 



19 



6 





76 



22 



11 



20 



28 



19 



6 





77 



22 



11 



20 



29 



19 



6 





78 



22 



11 



20 



30 



19 



6 





79 



22 



11 



20 



31 



19 



6 





80 



22 



11 



20 



32 



19 



6 





81 



22 



11 



20 



33 



19 



6 





82 



22 



11 



20 



34 



19 



6 





83 



22 



11 



20 



35 



19 



6 





84 



22 



12 



21 



36 



19 



6 





85 



22 



12 



21 



37 



19 



6 





86 



22 



12 



21 



38 



19 



6 





87 



22 



12 



21 



39 



19 



6 





88 



22 



12 



21 



40 



19 



6 





89 



22 



12 



21 



41 



19 



6 





90 



22 



13 



22 



42 



19 



6 





91 



22 



13 



22 



43 



19 



7 





92 



22 



13 



22 



44 



19 



7 





93 



22 



14 



23 



45 



19 



7 





94 



22 



14 



23 



46 



19 



7 





95 



22 



14 



23 



47 



19 



7 





96 



22 



15 



24 



48 



19 



7 





97 



22 



15 



24 



49 



19 



7 













Life cycle: Days. 



Maximum 24 



Minimum 16 



Average 19. 1 



Generations IV to VIII inclusive occupy roughly 16 days apiece 

 for development, and this period is the average life cycle during the 

 summer months. Some aphides will develop in 14 days and others 

 in 19 or 20. Table IV gives the life-cycle records of these five genera- 

 tions and also that of the ninth. The records in some instances are 

 small, but the fact that in the first five of these generations there is 

 practically no difference in the duration of the life cycle was cor- 

 roborated by a larger series of experiments during the summer months 

 with individuals of which the respective generations were unknown. 



