April, '14] HEWITT: THRIPS INJURING OATS 215 



It will be noted that in the percentages of "Abundance" given above 



there is practically no difference between the extent of the injury on 



the inside and outside rows of the plot, indicating an evenness in the 



distribution of the insect over the plot. 



"Abundance, Garton's Regenerated." Inside plot, outside row. 11 stems counted. 



Maximum sterile spikelets 38 . 8% 



Minimum sterile spikelets 6.4% 



Average sterile spikelets 17 . 3% 



"Banner H." Outside plot, outside i"o\v. 1.5 stems counted. 



Maximum sterile spikelets 55.2% 



Minimum sterile spikelets 3 . 5% 



Average sterile spikelets 29 . 5% 



"Bamier M." Inside plot, outside row. 19 stems counted. 



Maximum sterile spikelets 56 . 8% 



Minimum sterile spikelets 14 . 2% 



Average sterile spikelets 36 . 3% 



From the above results it will be seen that the most seriously in- 

 jured variety of oats of those examined was " Banner M," 19 inflo- 

 rescences of which variety had an average of 36.3 per cent, of sterile 

 spikelets. The variety least attacked was " Abundance Garton's 

 Regenerated," 11 inflorescences of this variety had an average of 

 17.3 per cent, of sterile spikelets. 



Reference has already been made to the greater liabilit}^ to thrips 

 injury of the late flowering varieties and the foregoing percentages 

 support this opinion. The " Banner " variety is one of our late 

 flowering varieties and both percentages and field observations showed 

 that it was more subject to the production of sterile spikelets by the 

 thrips. Mr. G. Hutton, who studied cereal crops in Alberta during 

 the summer of 1913, informed me that " Banner " oats suffered most 

 from sterile spikelets in Alberta where he noticed the occurrence of 

 " white-ears" in oats near Red Deer and Athabasca Landing, Alta. 



Description and Life History of Anaphothrips striatus Osborn. 



The insect and what is knowTi of its life history, etc., has been de- 

 scribed by Hinds from whose excellent account the following has been 

 mainly taken: 



The length of the female (Fig. 19) is 1 to 1.6 mm. The general 

 color is yellow with more or less dusky or brownish shading in some 

 parts. Hinds states that the male is unknown.^ I have never found 

 male specimens, although Gary (1902) describes the male. 



The eggs are reniform and vary in length from 0.265 mm. to 0.33 

 mm. and in width from 0.085 mm. to 0.145 mm. The full grown larva 

 is fusiform and about 1.2 mm. in length. 



1 Hinds has informed us th at he has found a few males since his memoir was written. 



