132 



MISCELLANEOUS PAPERS. 



All my aphides which were reared individually, in vials, were 

 wingless. Other aphides, however, of the same mothers, and placed 

 in cages containing many other aphides as well as a less abundant 

 food supply, often became winged. In Science, Volume XXI, Janu- 

 ary 27, 1903, pages 18—19, Prof. M. V. Slingerland gives an account 

 of rearing individually G2 generations of Myzus achijrantes during a 

 period of 2 years and 10 months, only wingless agamic females being 

 produced. From these and other evidences obtained it may be in- 

 ferred that the development of the winged forms among aphides is 

 largely caused by an insufficient food supply. 



The number of molts is invariably four, the time of occurrence of 

 the different molts being shoAvn in Table IV. 



Table IV. — Periods of molts of Aphis niaidi-rudicis, vivi parous (joicrution, 11)06. 



Date of birth. 



April 18 

 April 19 

 May 1 . . 

 May 4. . 

 May 13. 

 May 21 . 

 June 27. 

 June 28- 



Age at 

 birth of 



first 

 young. 



Days. 



As a rule, reproduction did not begin until the next da}^ after the 

 fourth molt, though it sometimes occurred within a few hours after 

 the molt. Often in the last generations, in autumn, rei^roduction 

 did not begin until two clays after the last molt. 



OVIPAROUS GENERATION. 



The oviparous generation was found in the insectary, in 1906, from 

 October 2 to December 21. Eecords of 17 individuals of this genera- 

 tion were obtained (Table V) ; the records, however, are not complete 

 in all cases. The length of the immature stage — from birth to 

 adult^ — varied from 10 to 39 days, this latter being a very exceptional 

 record. 



