Norman Cunliffe 111 



of their progeny. These flies were caged with new host plants to see 

 whether they were capable of producing another brood. In addition, 

 the first progeny were also caged with separate host plants in order that 

 the period between the emergence of Generations I and IP might be 

 determined. 



The data obtained from these cages are detailed below. 



Thirty of the parents were removed alive 28 to 31 days after the date 

 of the first infection (15. 5. 20) and used to infect oat plants grown under 

 a protective covering. In the three experiments the flies were provided 

 with sugar and water. 



{a) On the 31st day sixteen flies were placed on the ears of spring 

 oat plants, which flowered on the 32nd day. Copulation between one 

 pair was observed on the 43rd day, eggs being deposited in the glumes 

 on the 45th day. Twelve living parent flies were removed on the 45th 

 day. 



Result: no flies emerged and probably the larvae failed to mature 

 owing to lack of nutriment. 



{b) On the 32nd day, fourteen flies were placed on spring oat plants 

 not in ear. Copulation was observed between one pair on the 38th day 

 and five living parent flies were removed on the 45th day. 



Result: the first and last flies emerged on the 69th and 81st days 

 respectively, and the average period was 78-7 days (seven flies). 



(c) The eleven flies which were bred out about the 50th day were 

 placed on the ears of spring oat, being removed on the 65th day. 



Result: the first and last flies emerged on the 82nd and 85th days 

 respectively, the average period being 83-3 days (three males), i.e. 33-4 

 days after the emergence of their parents. 



The result of all these experiments is that, from parent flies of Genera- 

 tion III, adult flies of Generation I were obtained after approximately 

 50 days, and from the same parent flies of Generation III a second series 

 of adult flies of Generation I was obtained in 78-7 days. Also nine of the 

 original parents lived until the 50th day and one until the 59th day, 

 time enough to have produced yet a third brood under favourable 

 circumstances. 



1 In this paper, for convenience of reference only, the generations at present recognised 

 are numbered. I am convinced that further experiment will show that more than three 

 generations may be produced in the field. Generation I refers to the individuals which 

 pass through the stages, egg to adult in spring. Generation II to the individuals passing 

 through the same stages in the summer and Generation III to the individuals which hiber- 

 nate in the immature stages. In the following spring these individuals produce Genera- 

 tion I. 



