3<S 



PAPERS ON APHIDID^. 



Mr. R. L. Wobstor has followed the successive generations of 

 this species in the insectary of the IlUnois State Entomologist from 

 the eggs which hatched March 27 through nineteen generations to 

 October 18. The nineteenth generation disappeared before maturing 

 and the oviparous generation was not obtained. In liis expcM-imcnts, 

 reported by Dr. J. W. Folsom (1909), he found that the length 

 of time from birth to maturity varied from 5 to 24 days, with an 

 average for the season of 10 days, and the length of Ufe of an individual 

 varied from 9 to 43 days, with an average of 22. The largc^st number 

 of young produced in one day by a single female was 13. with a 

 yearly average of 3.7 young per day; the maximum number of 

 young born of a female was 75, the average for the series being 34.8 

 young per female. 



MOLTING. 



wSo far as our observations extend, the yellow clover aphis inva- 

 riably molts but four times. Table Y records the molting records 

 of six individuals from data obtained by Mi-. Parks in 1909 at 

 La Fayette, Ind. 



Table V. — Periods of molts of Callipterus trifolii, viviparous generation. 



Date of birth. 



Age at Age at 



first molt, i second 

 second \ molt, third 

 instar. instar. 



1909 



May 15 



May 20 



Do 



May 31 



Do 



Junes 



Age at 

 hirth of 



first 

 young. 



Days. 



10 

 11 

 11 

 9 

 8 

 10 



FECUNDITY IN RELATION TO OTHER SPECIES. 



In comparison with its associate on clover, Macrosiphum jnsi Kalt., 

 CaUipterus trifolii is quite noticeably less prolific. While pisi, accord- 

 ing to our 1913 experiments, produces an average of about 65 young 

 and a maximum number per female of 124 young, trifolii, on the 

 other hand, averages 50 young and produced a maximum of 99 young 

 per female. Likewise a single pisi has produced as high as 13 young 

 in one day while the maximum number of young per day borne by 

 a female trifolii was 9, and this was an unusual number. 



From dissections made in Illinois several years ago the writer 

 found that the oviparous females contamed an average of 10 eggs 

 per individual. The past fall (1913) 8 oviparous females were 

 examined and found to contain the following numb(M-s of apparently 

 fully developed eggs each, respectively: 13, 13, 14, 10, 12, 13, 14, 16- 

 an average of 13. 1 + eggs per female. In the latter counts only females 



