SHORTER ARTICLES AND DISCUSSION 



HEREDITY IN A PARTHENOGENETIC INSECT 

 (APHIS) 1 



Statement of Problem 



As is well known, Johanssen has found that in self-fertilizing 

 strains of beans selection within the strain — selection in the 

 " pure line " — does not change the mean of successive fraterni- 

 ties. If this conclusion holds generally we should expect it to 

 hold among parthenogenetic species also. Among asexually 

 reproducing animals Jennings (1909) finds that it is true for 

 Paramecium and Hanel (1907) for Hydra. 



Shull (1910) has found that strains of Hydatina from New 

 York differ from a strain from Baltimore in the rate of produc- 

 tion of males, and Whitney (1912) has found a similar differ- 

 ence in strains. For Daphnia (Woltereck, 1910) the persistence 

 of the mode is less easily determined because of a high degree 

 of variability depending on conditions. 



Insects seemed to offer a new field for /such studies, one in 

 which we might expect external conditions to play a smaller 

 role, and because of the well-known parthenogenesis of Aphids 

 and their availability it was determined to test so far as it could 

 be done in a few weeks of a summer, the suitability of plant lice 

 for studies of this sort. 



Material and Method 



After some experimenting it was decided to use Aphis rum wis, 

 an aphid that commonly infests the poppies and nasturtiums 

 about Cold Spring Harbor. 



Potted poppies and nasturtiums were kept growing in the 

 laboratory in large aquarium jars (about £ meter high) covered 

 with cheese cloth. Each plant was carefully inspected to make 

 sure that there were no aphids upon it. Then one gravid female 

 was placed on each plant and its movements and reproduction 

 carefully watched. All young in these summer broods were 

 produced parthenogenetioally. 



1 From The Biological Laboratory of the Brooklyn Institute of Arts and 



