122 Observations on the Habits o/Oscinella frit 



The results of the experiments of Series I give a mean of 35-5 days, 

 and this is the average period elapsing between the times of emergence 

 of consecutive generations in the summer. 



This period is the same whether the fly breeds on grasses or cereals. 



The experiments in Series II indicate an average period of 254 days 

 as the time required for the metamorphosis of the winter generation. 



The emergence of a second series of flies, after 63 days, in the last 

 three cages (Series I) is of interest. The average period between the times 

 of emergence of the first and second series is only 27-5 days, too short a 

 period for the time of year (September), to enable one to presume an 

 additional generation. On the other hand, taking the three cases, the 

 greatest length of life of an individual of the first series is 47 days and 

 the shortest interval between the death of the last parent and the earhest 

 emergence in the second series is 43 days; thus it would seem to be a 

 case of either deferred oviposition or the production of a second 

 brood. 



It has been proved therefore that frit-fly is able to utilise the following 

 grasses as host plants in the summer: Arrhenatherum avenaceum, Festuca 

 pratensis, Lolium italicum, L. perenne and Poa annua. 



In addition flies were reared in the spring of 1920 from the following 

 grasses which had been infected in 1919: Alopecurus myosuroides 

 (= agrestis), Arrhenatherum avenaceum, Hordeum. pratense, Lolium 

 italicum and Lolium perenne. 



Addendum. 



The following data indicate the extent of the infestation of two 

 common grasses and also that an absence of the typical sign of attack 

 does not necessarily mean the absence of the pest. No decided preference 

 for volunteer oat plants was apparent. 



Lolium italicum and volunteer oat plants from plot C (Fig. 1) were 

 collected on 11. 3. 20. Plants were picked at random about every 3 feet, 

 to the number of about 150 for each species, and carefully examined. 

 Control plants produced frit-fly in the first half of May. 



c/n of larvae "/o plants showing 



in stems typical sign of 



Signs of showing no attack but no 



No. of "/o larvae boring-larvae sign of trace of frit 



plants found absent attack boring 



Lolium italicum 170 8-2 Nil 43 14-8 



Volunteer oat 149 10-8 „ 29 9-2 



The plants referred to in the last column showed the dead central 

 shoot typical of frit attack, and cursory examination in the field would 

 have led one to suppose that the frit-fly was the cause of the damage. 



