MICHIGAN ACADEMY OF SCIENCE. 113 



H. S. Jenniugs of the Johns Hopkins University for the privileges extended 

 to me wliile there, and to Dr. C. B. Davenport, Director of the Station for 

 Experimental Evolution, Cold Spring Harbor, Carnegie institution of Wash- 

 ington, for the opportunity to continue the work into the summer months. A 

 full account is to be published. 



Alma College, Alma, Michigan. 



SEX DETERMINATION IN THE WHITE-FLY ALEURODES. 



NORMAN B. STOLL. 



In 1917 Williams, in the Journal of Genetics, suggested that Aleurodes 

 vaporariorum, the common "white-fly" of the green-house, is a form in which 

 males are produced (in the American members of the species) from both unfer- 

 tilized and fertilized eggs, while females come from fertilized eggs only. 

 Experiments to test this conclusion by breeding flies from Ann Arbor green- 

 houses showed that 



(1) the progeny of virgin females are exclusively males, and 



(2) females were found in large majority in some cultures of mated 

 mothers. 



On the basis of the law of chance it can be shown that the probability of 

 the high female ratios referred to in No. 2 is so exceedingly small as to be 

 regarded as impossible, if selected from a population in which males and 

 females were produced in equal numbers. The conclusion is drawn that 

 females come only from fertilized eggs, males only from unfertilized eggs; but 

 that mated females may lay unfertilized eggs, as well as fertilized, as in the 

 honey-bee. 



(Complete paper to be published in Genetics.) 



Junior College, Detroit, Michigan. 



