16 THE REPORT OF THE No. 36 



The tables, as a whole, indicate clearly some interesting general correlations. 

 The first and most important is the fact, as shown in Table I, that a large pro- 

 portion of the larvae come to the surface when ploughing is done early in the 

 season. Even when ploughed as late as September 28, 85.36 per cent, of the 

 larvae left the buried material. The later ploughings were markedly less effective 

 in this respect, the operation but a week later causing but 61.36 per cent, to 

 come up. Oddly enough the experiment of October 12, two weeks later, was 

 somewhat more effective than that of October 6, 67.53 per cent, of the larvae 

 being recovered at the surface. With the four later ploughings the proportion 

 attaining the surface decreased still further, so that for the study started on 

 October 19, 29.87 per cent., from that of October 26, 12.5 per cent., from that 

 of November 2, but 10 per cent., and from November 9, 12.5 per cent, were 

 recovered. The last two studies dealt with relatively small numbers of larvae, 

 and the value of the figures should be discounted somewhat. 



The second important point, as shown in Table I, is that the first week 

 following ploughing is the most important in respect to the numbers of larvae 

 coming to the surface. This is particularly true in the early season when the 

 soil is warm. As the season advances a progressingly decreasing proportion 

 moves in the first week and the proportion coming up -on the second and third 

 week increases. These late moving larvae in an early fall would be very apt 

 to be retained underground by the rapid cooling of the soil. 



The reaction of the larvae below ground in the spring was studied somewhat 

 sketchily in the same way in 1922. The larvae were recovered at the surface 

 in traps in fairly large numbers both from material ploughed down in the spring 

 of 1922 and also from a field ploughed late in the fall of 1921. 



The general reaction of the larvae was very similar to that in the fall, though 

 the activity following immediately after turning down was not at all character- 

 istic of the spring conditions.' Warm rains on the other hand in early May 

 were followed by very prompt appearance at the surface of relatively large 

 numbers of larvae. 



The larvae which were below ground all winter came through surprisingly 

 successfully. A characteristic count demonstrated a mortality of 11.1 per 

 cent, in stalks and 26.8 per cent, in stubble below ground, while the material on 

 the surface of the same field suffered comparatively lightly, the death rate 

 in stalks being 5.76 per cent, and that in stubble lying on the surface but 4.65 

 per cent. The spring studies were not prosecuted with the thoroughness of the 

 fall operations, and it will not be till the summer of 1923 that a detailed knowl- 

 edge of the reaction at this season will be available. 



That the larvae in Ontario in an essentially one-brooded area actually 

 come to the surface in important proportions when ploughed down in the fall, 

 and that this proportion increases with earliness of ploughing, has been clearly 

 demonstrated. What, however, becomes of these larvae after being brought 

 to the surface is not at all clear. For the most part they simply disappear, all 

 trace of the bulk of them so far being lost. 



The subsequent history of these larvae is a most important matter and has 

 been given a great deal of study both by the Federal and Provincial investigators, 

 with as yet very little definite result. This study has shown that beetles, ants 

 and even birds in the fall, account for relatively few, as none of these predators 

 are particularly active. The missing larvae could not be found among the clods 

 of soil on the surface of the ploughed area, they did not again dig into the soil 

 having once come to the surface, nor could they even be demonstrated in the 

 grass about the margins of heavily infested fields after ploughing, either in 1921 

 or 1922. 



