1907.] The Black Currant Gall-Mite. 587 



their green colour, later becoming brownish, dry, gall-like 

 bodies, more or less open at the apex. Other buds not so 

 badly infested as those above mentioned put forth diminutive 

 shoots and small leaves. As the disease increases by spreading 

 to more buds, it is noticed that owing to the failure of infested 

 buds to leaf, next year's buds are prematurely forced into 

 development, and so the plant's vitality becomes reduced. If 

 this continues, as it usually does, the plant is soon unable to 

 respond to the excessive drain upon it, the food stores become 

 used up, and ultimately the plant dies. 



It sometimes happens that a badly infested tree, by reason 

 oi the few buds left, or that the plant is capable of developing, 

 becomes after a year or two almost free from mites, but as soon 

 as any number of buds commence to develop they are rapidly 

 tenanted by mites and the plant very quickly dies. 



Life-History. — Very briefly the life-history may be sum- 

 marized as follows : — 



If an infested bud of the black currant plant be opened 

 about the middle of March it will be found to contain nume- 

 rous mites and eggs ; and if the temperature is favourable, 

 mites may be seen crawling at the bases of the buds and on 

 the stem, these having been forced to quit the partially infested 

 buds, which now commence to germinate. Most, if not all, of 

 these mites die. Towards the middle of April or early in May 

 the 'mites commence to migrate from the abortive buds, and 

 this continues through May, attaining its maximum towards 

 the end of the month and gradually becoming less and 

 less until the middle of June. During the latter part of 

 May and the earlier part of June the mites may be found all 

 over the stems, and early in June they commence to make 

 their way into the new buds. Of the many thousands which 

 leave the old buds, only a very small proportion reach the new 

 buds. But most of the migrating females are full of eggs, and 

 these are laid soon after an entrance is effected in the new 

 bud. After about twelve or fourteen days eggs and mites in 

 all stages of development are present in the centre of the bud, 

 and the latter now commence to work their way outwards. 

 They have not, however, been seen to leave the buds until early 

 in August, and then only in small numbers, and were last 



