168 Host Plants o/Oscinella frit among Grasses 



Experiments IV and V gave minimum, maximum and mean periods 

 of 42, 73 and 58 days (55 flies) between the times of emergence of con- 

 secutive generations in the spring, confirming the figures obtained in 

 1920. 



The foregoing records indicate that O.frit in captivity does show some 

 preference for Arrhenatherum species among the grasses and oats among 

 the cereals, although owing to the small yields no comparative measure 

 of preference has resulted. 



Additional observations on the prevalence of the fly in the field, 

 collected during the year 1921 indicate that for the years 1919 to 1921 

 during which the meteorological conditions were very different, the 

 periods of high and low prevalence tend to be constant. If this con- 

 clusion is supported by another season's observations, it will probably 

 render possible an explanation of the fact that early sown crops suffer 

 least damage. 



REFERENCES. , 



(1) CuNLiFFE, N. (1921). "Preliminary Observations on the habits of OscineUn frit, 



Linn." Ann. App. Biol, viii. No. 2, 105-134. 



(2) Miles, H. W. (1921). "Observations on the Insects of grasses and their relation 



to Cultivated Crops." Aim. App. Biol, viii, Nos. 3 and 4, 170-181. 



{Received March lUh, 1922.) 



