R?:SEARCHES AT WISLKY. 



165 



Much careful and valuable work bearing on the life history of the 

 black currant mite has been done in this and other countries ; such work, 

 owing to incapacity, I neither attempted to extend nor to corroborate. 

 My ideal was of a much lower standard, and was entirely confined to 

 discovering some practical means for preventing the mites from injuring 

 black currant bushes. It is for the grower of black currant bushes to 

 decide whether I have been successful in this attempt or otherwise. 



As a starting point it was important that I should become acquainted 

 to some extent with the habits and mode of life of the creature against 

 whom I was conspiring. I quite believe that all I observed, and more 

 also, has been recorded before. Therefore I do not claim originality for 

 any statement made ; I only conducted certain experiments because it is 

 both interesting and instructive to observe things oneself. 



Experiment I. — Much valuable information as to the ways and doings 

 of the mites can be obtained by placing a branch bearing a few 

 " big-buds " in a cylinder of very thin glass, and plugging the two ends 

 with cotton-wool (fig. 37). Within twelve hours the inner surface of the 

 glass cylinder vdll be covered with a teeming multitude of mites, and, as 

 the thin glass of the cylinder will permit the use of an objective magni- 

 fying four hundred times, the movements of the mites can be followed 

 with ease and certainty. When in their best condition for walking — 

 that is, soon after incarceration — the mites travel with amazing rapidity, 

 passing across the field of the microscope in an instant. After being 

 imprisoned for some days their movements become sluggish, and at the 

 end of a week most of the mites are dead, but still adhering to the inner 

 surface of the cylinder. In addition to the ordinary method of loco- 

 motion certain mites suddenly assume a vertical position, appearing as if 

 they were attempting to balance themselves on their tails. While in this 

 position the entire body sways slowly to and fro, describing a semicircle. 

 After repeating this movement several times, if not approached by another 

 mite, they suddenly leap into space out of the field of vision. If another 

 mite approaches the two come in contact in the upright position, 

 apparently a sexual act. 



If a glass cylinder containing mites is immersed in crushed ice, those 

 mites that are on the inner surface of the glass are killed within twenty 

 hours, whereas mites that are in the buds remain alive after four days' 

 exposure to such treatment. 



Chloroform and ammonia respectively kill mites both on the glass and 

 in the buds within twenty-four hours. This experiment, however, has no 

 practical application. 



The mites are almost colourless and very minute, rarely exceeding 100th 

 of an inch in length (fig. 38). 



Experiment II. — A black currant shoot having a terminal and two 

 lateral buds, free from mites, was procured ; two " big-buds " were carefully 

 fixed to this shoot by means of " seccotine " below the lowermost healthy 

 bud. The cut end of the shoot thus prepared was placed in water and the 

 whole covered with a bell jar. 



After an interval of twelve hours numerous mites had moved from the 

 "big-buds" and were present on the shoot, and more especially in the 

 axils of the healthy buds. On dissecting one of the healthy buds it was 



