6 BULLETIN 261, U. S. DEPARTMENT OE AGRICULTURE. 



Table I. — Length of pupal period of wintering larvse of the plum borer, Winchester, Va., 



1913. 



No. of 

 obser- 

 vation. 



Date of— 



Length 



of 

 pupal 

 period. 



Pupa- 

 tion. 



Emer- 

 gence. 



1 

 2 



Apr. 14 

 14 



May 17 

 15 



Days. 

 33 

 31 



3 



17 



15 



28 



4 



19 



16 



27 



5 



19 



21 



32 



6 



22 



21 



29 



7 



24 



18 



24 



8 



24 



21 



27 



9 



24 



21 



27 



10 



24 



21 



27 



11 



25 



24 



29 



12 



25 



27 



32 



13 



25 



27 



32 



14 



26 



27 



31 



15 



26 



27 



31 



16 



17 



May 2 

 2 



27 

 27 



25 

 25 



18 



4 



June 2 



29 



19 

 20 



4 

 5 



May 30 

 June 2 



26 



28 



21 



6 



2 



27 



22 



6 



2 



27 



23 



7 



3 



27 



Maximum 



33 



24 



M 



nimum 







zerage 





Ai 



28. 43 









The longest pupal period observed was 33 days, the shortest 24, 

 and the average of the 23 observations 28.43 days. The records at 

 Winchester show a slightly longer duration of this stage of the in- 

 sect's life than has been observed by others, though data from other 

 sources are rather limited. Girault, in 1905, notes that one larva 

 pupated in the rnsectary at Washington March 28 and emerged 

 April 21, a period of 24 days, while Rosenfeld, at Myrtle, Ga., in 1906, 

 reports one insect that transformed from larva to adult in 20 days. 

 Fred Johnson, at Youngstown, N. Y., in 1905, has the following note: 

 " Larvse confined in jar form cocoons June 28. Adults emerged from 

 these July 20 and others continued to appear until August 4." Evi- 

 dently some of the insects in this instance transformed in less than 

 23 days. The weather conditions of the spring of 1913 may be 

 partially the cause of the longer pupal period at Winchester, the 

 unusually high temperature prevailing through March hastening the 

 insect's pupation, while the relatively cold April that followed prob- 

 ably delayed the emergence of moths. 



EMERGENCE OF SPRING BROOD OF MOTHS. 



Table II gives in detail the time of appearance of 79 moths that 

 emerged at Winchester in the spring of 1913 from field-collected 

 rearing material. The first adult appeared in the laboratory on 

 April 25 and by the fore part of May the insect was emerging in 

 numbers. 



