Insects, etc., Injurious to the Plum. 



389 



Edwards (6) does not appear to have been acquainted with the 

 economic literature of this subject, for he states in Ins work on the 

 Hemiptera-Hornoptera of the British Isles (p. 3) that " none of the 

 Homoptera-Oicadina can be said to be of any economic importance 

 in Britain ; certain species, as Pliilccnus spnmaria, Chlorita viridula, 

 Enjitcryx auratus, etc., sometimes swarm in gardens, and elm and 

 beech trees are generally tenanted by countless numbers of Typhlo- 

 cylndcv, but it does not appear they do any real harm in any stage." 



The Typhlocybidce are small leaf hoppers, which form a very 

 homogeneous group, and some, such as 

 the Typldocybu quercus, are very gaily 

 coloured ; others, as the two Chloritw, 

 are more uniform in appearance. 



No less than twenty species of 

 Typhlocyba are known to occur in 

 Britain. One species is described from 

 plums (T. priiid, Edw.), another from 

 nuts (T. avcllancc, Edw.). Neither of 

 these have been so far observed by me 

 on fruit trees in any numbers, and in 

 many orchards and plantations visited 

 none could be found at all. 



It is strange that one of the species 

 that has done so much harm to fruit 

 trees should be an oak feeder. At 

 least, it has been identified as such by 

 Mr. Distant, and it certainly answers 

 the description of Typhlocyba quercus 

 given by Edwards, although his figure 

 does not quite agree with any specimen 

 I have. The series in the Douglas 

 and Scott collection in the British Museum, however, all agree with 

 those that have been sent me. 



The damage done by these leaf hoppers is very marked, and has 

 been referred to by various writers abroad. 



In the case of apple and plum the insects, by means of their 

 probing proboscides constantly being inserted into fresh tissue and 

 constantly sucking out the sap, produce on the leaves, first, minute 

 pale spots, which gradually increase until the leaves become more or 

 less entirely silvery green, or grey, or marbled. To such an extent 

 have I seen this effect that anyone would have thought, at a distance, 

 that the trees were suffering from Silver Leaf disease. 



FIG. 259. DAMSON SPRAY, SHOWING 

 DAMAGE BY LEAF HOPPERS. 



Note pale silvery hue of leaves. 



