4 A STUDY OF NATURAL METHODS OF 



The shaded area on the plan of the estate (Fig. 1) shows the distribu- 

 tion of these pests in normal years, and it will be noted that there appears 

 to be a definite relation to the prevailing winds, as indicated by the 

 arrows. This sketch, too, is especially interesting since it appears to 

 demonstrate that the beetles do not usually fly much over half a mile 

 from the feeding trees to oviposit. Thus it will be observed that the 

 inner limits of the shadow conform fairly well to the contour of the culti- 

 vated area on the infested side of the estate, and, furthermore, that there 

 is no destruction in those fields that lie along the south-western portion, 

 even where feeding trees are adjoining. Another interesting feature is 

 the unshaded area about the quarters, adjoining the horse paddock. 

 I have called attention to this area in my reports, because it was most 

 remarkable to find such a spot without grubs right in the midst of the 

 worst-infested fields. I finally came to the conclusion that this immunit}^ 

 was due to the beetles being destroyed by the hundreds of fowls, especially 

 during the morning flight, when the gravid female beetles rest upon the 

 cane leaves for a considerable period before descending to lay their eggs, 

 at the roots of the plants. This hypothesis would appear to be correct 

 for just before the 1920 flight of the beetles all the foAvls had been dis- 

 posed of, hence the beetles escaped and, naturally, the grubs covered this 

 former immune area, furthermore, as indicated by the small circles, we 

 were unable to find any disease organisms there, as was the case in other 

 unshaded areas shown by the sketch. 



In the early days this land was used for gro^\dng bananas ; and I 

 have learned that when planted to sugar-cane, in 1904, there was no 

 noticeable injury from grubs. The 1905 crop was certainly a tremendous 

 one, for it ran well over 30,000 tons. The third year, however, grubs 

 began to give trouble, and there has been no material let-up ever since, 

 the last year being the worst of the lot, with a harvest of only 2,400 tons. 

 The shortness of this latter crop was due to the abnormal distribution of 

 these pests, for many of the beetles flew far past their old limits in the 

 shaded area, to deposit their eggs in the normally immune portion of 

 the estate, indicated on the sketch by stippling. 



It is possible that this erratic flight of the beetles was largely due to 

 the terrific cyclone, which occurred on the night of 2nd February, just 

 about a fortnight after the main emergence of the beetles, hence just at 

 the time when they were ready to oviposit. Naturally, this gale would 

 carry them far past their normal locations ; at any rate, after studying 

 the problem from every angle, it is the only explanation that suggests 

 itself to me, and it appears to fit the case perfectly. 



A Study of Conditions under which the Muscardine Fungus 



IS Effective. 



On 10th August, 1917, we started experiments in the laboratory to 

 determine the relation of temperature and moisture to mortality from the 



