1907.] The Black Currant Gall-Mite. 589- 



" standing on end, and motionless, except for the waving of 

 their legs." They obtain a firm hold with the tail-disc and 

 seem to wait three or four minutes in this position hoping to 

 attach themselves to some insect or arachnid. The same author 

 also draws attention to a method they have of leaping. When 

 this work was first commenced I was often puzzled to find, that 

 when examining the mites under the microscope, they often 

 suddenly disappeared from the field of vision ; this happened so 

 frequently and so rapidly, that I came to the conclusion that 

 those mites which were standing upright were capable of 

 suddenly throwing themselves forward by the action of the tail- 

 disc. Mr. Warburton mentions that the longest distance covered 

 by a leap measured four millemetres, but I have frequently seen 

 this distance increased by two or three millemetres. 



In addition to these three methods, I have noticed that at 

 times the mites will roll the abdominal portion over towards the 

 head, and lying on their backs with their legs actively waving,, 

 will remain so for one or two minutes, and then suddenly 

 straighten themselves again with such force as to carry them 

 two or three millemetres. 



Varieties of Plants Attacked. — It has been thought by some 

 observers and growers that certain varieties were practically 

 immune, but I cannot say that my experience lends any support 

 to such views ; on the other hand, I have taken mites from the 

 Baldwin and transferred them to most of the known varieties, 

 and also from infested specimens of these varieties which have 

 been sent to me and infected others. Mr. E. J. Lewis 'states 

 that he has never found the old varieties to be attacked in 

 Kent.* 



Remedial Measures. — The suggested remedies are numerous, 

 but up to the present time none excepting the lime and sulphur 

 have resulted in exterminating the mite or diminishing the 

 disease to any appreciable extent. 



The various remedial measures may be considered under four 

 heads, viz. (i.) fumigation, (ii.) spray fluids, (iii.) natural enemies, 

 (iv.) miscellaneous. 



(i.) Fumigation. — Fumigation with hydrocyanic acid gas has 



Op. ciL, p. 10. 



