Insects Injurious to the Apple. 171 



VARIETIES OF THE MUSSEL SCALE. 

 There are four well-known varieties : 

 (i.) Variety vitis Goethe, found on the grape vine in England, 



Egypt and Germany. 



(ii.) Variety uhni Douglas, found on the furze (Ulcx cv.ropceus). 

 {iii.) Variety Candida Xewstead, on hawthorn in England. 

 ,{iv.) Variety japonica Kuw, found on Abies firma in Japan. 



PREVENTION AXD TREATMENT. 



The prevention of Mussel Scale is difficult, as it is undoubtedly 

 to some extent spread by birds and insects. We can, however, guard 

 against its importation with young stock by fumigating it, before 

 planting, with hydrocyanic acid gas. 



One of the best remedies is paraffin emulsion. This may be used 

 as a winter wash strong enough to kill the eggs under the scales, or 

 as a summer wash in the dilute form to kill the freshly hatched 

 young. Caustic alkali wash is also found successful by Furley (3). 

 More recently the Woburn w r ash has been found to act quicker than 

 either paraffin emulsion or caustic soda alone. The following account 

 taken from one of my reports (4) may be quoted here : 



" It may here be mentioned that some 2,000 odd trees were treated 

 in all at Mr. Amos' plantations. Some of the trees were completely 

 coated with the scale so that no bark could be seen. The majority 

 had but few coccids higher than the forks of the trunk, and all had 

 an immense quantity where any band of straw or cloth had been 

 used for staking purposes. In many trees the straw clasps seemed to 

 act as a check to further advance up the tree. A few trees showed 

 but a normal number of scale except under these protections. Erequent 

 observations proved that both Blue Tit (Parus cceruleus) and Long- 

 tailed Tit (P. caudatus) had done good work and the bands alone 

 protected the scale from them. The scale insect had sprung into 

 such vitality that thousands more of these useful birds could have 

 made no difference however. The orchard was partly down to grass, 

 partly cultivated beneath with gooseberries and black currants, and 

 partly cultivated without any bush fruit beneath. 



" The apples in the plantations were the following varieties : 

 Beauty of Bath, Ecklinville, Newton Wonder, Cox's Orange Pippin. 



" Two points in the attack were noticed : (1) that the trees on the 

 cultivated land were attacked more than those on the grass land, and 

 (2) that the thin skinned varieties were more damaged than the 

 thick. The latter is readily understandable, but the former is not, 



