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plants 14-4 per cent, and that of the dried ones 12-2 per cent. less. The 

 investigations were repeated with plants taken when ripening, and it 

 was found that the number of grains in the ears of the damaged plants 

 was 15-5 per cent, less than in the ears of healthy ones, and that the 

 absolute weight was 3-4 per cent, less ; the number of ears was also 

 less, owing to the absence of three-eared plants, and the smaller 

 number of two-eared ones. The ripening of the grain of the 

 damaged plants is delayed as compared with the healthy ones, which 

 is due to the fact that only the later stems are able to yield grain, 

 the earlier ones being destroyed. It is concluded that the injury 

 by C. genitalis decreases the harvest of summer-sown wheat by 

 about 40 per cent., which figure is called the " coeflS.cient of injury" 

 of these insects. 



Only the later samples showed injury due to Oscinella frit. Healthy, 

 but infested plants compared with uninfested ones showed an increase 

 in tillering of 176 per cent., an increase in the average length of the 

 stem of 1-5 per cent., an increase in the weight of the green plant of 

 12-6 per cent., and an increase in the weight of air-dried plants of 14-5 

 per cent. ; the plants infested by both insects showed in comparison 

 ^\dth those infested by C. genitalis only, an increase in tillering of 

 0-9 per cent., an increase in the average length of the stems of 6-2 per 

 cent., an increase of the weight of the green plants of 8'2 per cent., 

 and the dried ones of 11 per cent. 



Similar effects by 0. frit on samples of barley, which is not injured 

 by C. genitalis, are illustrated by tables. Samples of barley taken 

 during the harvest showed that the plants injured by this pest exhibit 

 an increase in the green \veight and in the number of two-eared and 

 three-eared plants. The absolute weight of the grains of injured 

 plants had somewhat decreased, but this may be due to the more 

 profuse tillering and to the later ripening. 



It is concluded that the Frit fly does not cause any serious changes 

 in the attacked plants, at least in the case of summer crops, sown at 

 a normal time. In the case of late-sown crops, the Frit fly infests 

 the first stem and the results on the plants are the same as those caused 

 by C. genitalis. When the crops are sown at the normal time, the 

 insect breeds on the side-shoots, mostly on that part of them which 

 appears later. Thus there is sufficient material for the insect to breed 

 without injuring the plant and its yield. Both in the case of sunmier- 

 sown wheat and of barley, about 40 per cent, of the side-shoots perish 

 when infested by Frit fly, thus increasing the vigour of the main stem. 

 This fly, while injuring the side-shoots, has the same effect as a gardener 

 who pinches the shoots and thus directs the juices of the plants towards 

 the formation of fruit. If that is so, this insect, when attacking 

 summer-sown crops to a degree not exceeding 40 per cent., may 

 possibly be regarded as a useful insect. Further researches are, 

 however, required to confirm these conclusions. 



During the discussion, Professor N. Kulagin pointed out that the 

 tillering of barley depends also on the local meterological conditions ; 

 S. Soloviev reported that the Frit fly is very injurious in the 

 Government of Petrograd, where it appears on early crops in the 

 second half of April ; A. Silantiev and A. Baranov recorded that in 

 Northern Russia this insect attacks the main stem of the plant and 



