242 Insect Pests. 



of insects which may possibly prey upon JiJ. ribis, Lewis mentioned 

 a dipterous larva as being commonly met with. This larva was 

 often seen in " big buds," but it fed slowly and the mites increased 

 so rapidly that it did no good. Concerning this larva, which is the 

 maggot stage of a two-winged fly, the late Miss Ormerod mentioned 

 some years ago (9) that " there appears to be no doubt that it was 

 feeding upon the Phytopti." 



Lewis also says : " I have noted certain species of Thrips, and 

 various insects belonging to the Collenibola, a sub-order of the Aptera, 

 but though many of the former are predaceous and are known to feed 

 on Curculio eggs and Phylloxera (10), the latter, so far as I know, feed 

 only on refuse animal and vegetable matter, and were doubtless 

 chance visitors from the old diseased dried-up buds, filled with the 

 remains of the gall mites originally infesting them. 



" Acari are numerous in the diseased buds, among those met with 

 being a species of Tetranychus closely related to the red spider, and 

 two species of the genera Tyroglyphus and Sejus ; the former genus 

 belonging to the family of the cheese mites, and the latter to the 

 Gamasidm, a family of mites which are parasitic on insects. I have 

 often found representatives of these two genera in the buds of the 

 hazel infested with E. avellanm, and Mr. Theobald quotes them as 

 being found in buds attacked by the yew mite. I have often noticed 

 outside the diseased buds numbers of a species of Bi-yohia." 



Lewis also considers that beetle mites (Oribafida') devour many 

 of the Eriophyes when they are migrating, and states that "they 

 have also been noticed devouring the galled patches on plum leaves 

 attacked by the plum mite." None of the above-mentioned mites 

 and insects can prey upon U. ribi^ to any great extent, as they 

 produce no lessening in the spread of this disease. 



Some small Ghalcididm have also been bred from this Eriophyes, 

 and Collinge(13) records the Seven-spotted Ladybird {CoccincUa 7- 

 punctata) as an enemy. 



Pkevention and Teeatmext. 



So much has been said and ^vritten on this subject that it is 

 impossible to enter into all the various supposed remedies. 



At present all that can be said is that we know of no means of 

 destroying this serious pest. Several things, however, can be done to 

 check it : — 



(1) Cultivation from clean sioch is first to be borne in mind. 

 Clean stock can be obtained, especially from abroad. The French 

 varieties are, we may say, free from this mite, and, moreover, 



