INSECTS 215 



calcium sulphide, and some little by the paraffin emulsion ; but 

 neither of these had affected the mites ; and, even in cases 

 where the bushes had been cut down before treatment, the new 

 growth was found to be heavily infested. 



In the following season further series of experiments were 

 conducted, monthly applications of the following substances 

 being made- 

 Methylated spirits, 50 per cent. 

 Naphtha. 



Naphthalene in naphtha. 

 Formalin, 2, 0-5 and o-i per cent. 

 Paraffin. 

 Paraffin emulsions, 40 and 20 per cent. 



but in no case was any effect on the mites observed. It was 

 noticeable in these experiments that the undiluted paraffin did 

 much less harm to the bushes than the strong emulsion, a fact 

 which has been observed in other cases as well (p. 155). 



That bushes which had been cut down before treatment 

 should produce new growth infested by the mite, was strongly 

 suggestive that the insect might harbour in the ground, or 

 elsewhere than in the buds ; but a careful examination of the 

 stools, and of the earth in contact with them, failed to reveal 

 any signs of it. A number of experiments were then made in 

 which batches of bushes which had been cut down, and soaked 

 for various lengths of time in a mixture of equal volumes of 

 methylated spirits and water, were replanted, either in different 

 situations in the farm, or in ground at Harpenden and St. Albans 

 where no mite existed. In the latter case the bushes remained 

 quite free from mite, whereas with those replanted in the farm, 

 the new growth was slightly affected, and to an extent dependent 

 on the proximity of already infested bushes. Thus it appears 

 that the mite harbours nowhere but hi the buds, and that its 

 appearance in the new growth is due simply to re-infection. It 

 was noticeable in these cases that an immersion in the diluted 

 spirits, even for six hours, did not injure the bushes much, so 

 long as they were left exposed sufficiently for all the alcohol to 

 evaporate before they were replanted. 



Cutting down the bushes in a plantation is, however, not 

 sufficient to ensure the eradication of the disease, presumably 

 because some buds may be overlooked or left on the ground, 

 or possibly because some mites may exist even in dormant 



