THE POTATO TUBER MOTH. 



29 



1st Gen. 



Plot B. 

 2nd Gen. 3rd Gen. 



4th Gen. 



5th Gen 



Jan. Feb. 



Mar. 



Apr. May. June. July. Aug. 



Sept. 



Oct. 



Nov. Dec. 



The gradual emergence of adults from a generation the larvse of 

 which aU hatched on the same day may be shown from the examples 

 which follow, one from midsummer and the other from midwinter. 



Table 8. — Emergence of adults of the 'potato tuber moth from two generations, the eggs 

 of one hatching on July 7 and those of the other on December 8. 



Average mean temperature 72° F. 



Average mean temperature 61° F. 



1914 





1914 



July 7. 



Eggs hatched. 



Dec. 8. Eggs hatched. 

 1915 



Aug. 1. 



2 adults emerged. 



Mar. 7. 2 adults emerged. 



Aug. 3. 



21 adulta emerged. 



Mar. 9. 4 adults emerged. 



Aug. 5. 



18 adults emerged. 



Mar. 10. 2 adults emerged. 



Aug. 6. 



4 adults emerged. 



Mar. 11. 1 adult emerged. 



Aug. 8. 



1 adult emerged. 



Mar. 12. 6 adults emerged. 



Aug. 10. 



2 adults emerged. 



Mar. 13. 3 adults emerged. 



Aug. 11. 



adults emerged. 



Mar. 14. 3 adults emerged. 

 Mar. re. 1 adult emerged. 

 Mar. 18. 4 adults emerged. 

 Mar. 20. 1 adult emerged. 

 Mar. 23. 1 adult emerged. 

 Mar. 30. adults emerged. 



The records given above show plainly the difference in number of 

 generations which may be caused by taking the first to emerge or the 

 last to emerge in each life cycle. If the first eggs deposited by the 

 "first to emerge/' and the last eggs deposited by the ''last to emerge" 

 are taken for the second generations, the difference wiU be increased 

 to such a degree that almost a month will elapse between the time 

 of starting the two generations. 



Taking generations throughout the year gives the following periods 

 (Table 9). The records are for 1914, and were made at Pasadena, Cal. 



Table 9. — Variation in life cycle of the potato tuber moth. 



January. .. 

 February.. 



March 



Aoril 



•Vlay 



June 



July 



AUKU.St 



September. 



October . . . 

 November. 

 Dccftmber. 



Month started. 



1914. 



I9i;j. 



Eggs 

 laid. 



Jan. 4 

 Feb. 11 

 Mar. IH 

 Apr. if) 

 May 1(1 

 Juno 14 

 July i:i 

 Aug. 17 

 Sept. 14 



Oct. 14 

 Nov. 7 

 Dec. 12 



Adults emerging 



First. 



Apr. 

 Apr. 

 May 

 June 

 July 

 July 

 Aug. 



S<!J)t. 



Oct. 



Dec. 24 

 Feb. 7 

 Mar. 19 



Last. 



Apr. 30 

 May 13 

 May 31 

 Juno 20 

 July 10 

 Aug. 3 

 Aug. 23 

 Sopt. 27 

 Nov. 10 



.Tan. 14 

 Fob. 22 

 Apr. 10 



Greatest 

 number 

 emerg- 

 ing. 



Apr. 10 

 Apr. 29 

 May 21 

 Juno 12 

 July 7 

 July 27 

 Aug. 17 

 Kept. 22 

 Nov. 1 



Doc. 31 

 Jan. 13 

 Mar. 25 



Length 

 of life 

 cycle. 



Bays. 



91 

 73 

 01 

 55 

 49 

 40 

 33 

 33 

 45 



71 



92 

 97 



