Norman Cunliffe 109 



Table II (1920). 



In ''Remarks" column, D=sun obscured. 



S =sun not obscured. 

 Number = velocity of wind in miles per hour. 



Observations in the Insectary. 



Controlled breeding experiments, with field material, were conducted 

 to ascertain the relationship between the periods of high prevalence in 

 the field and the production of successive broods or generations. 



The environmental conditions inside the cages were artificial, ex- 

 cessive moisture and close confinement being unfavourable factors whilst 

 protection from direct sunlight and the presence of a plentiful food supply 

 were favourable factors. Therefore the period between the dates of the 

 infection and the emergence of the flies of the next generation may be 

 only approximate to the natural period. 



Method. 



Fhes were collected in the field on 15. 5. 20 and used to infect various 

 cereals which had been grown under protective covering. In each case 



