INSECTS 205 



emulsions were examined, such as the character and propor- 

 tion of the soap used, and the nature of the oil. Out of five 

 brands of soap examined, four gave practically the same results, 

 and the proportions used could be reduced without detriment 

 from the I per cent, taken in the above series, to o'3 per cent. ; 

 whilst any oil, so long as it was not more volatile than an 

 ordinary lighting oil (used in the above series) gave equally 

 good results, the heavier oils, however, producing such results 

 more rapidly. A subsequent examination of the action of these 

 caustic washes in removing moss from trees showed, however, 

 that for that purpose the proportion of alkali must be increased 

 up to 2 or 2j per cent, of soda, and with such an increase, and the 

 substitution of iron sulphate as an advantageous substitute for 

 soap in emulsifying the oil, the winter wash for which the formula 

 has been given on p. 160, has been advocated (VI, 87 ; VIII, 46). 



This wash has been in use at Woburn for ten or twelve years, 

 and both as regards mussel scale, as well as other pests, it seems 

 to have been eminently successful. The mussel scale which 

 was very prevalent throughout the ground, has practically dis- 

 appeared; indeed, afterlts first application, the scale had been so 

 effectually destroyed, that sufficient was not found for further 

 experiments on the subject, and material had to be obtained else- 

 where. For cleansing purposes it need be applied only once every 

 three years. 



Its effect is more satisfactory when the date of its application 

 is deferred as long as possible : one series of experiments (VI, 133), 

 for instance, giving 



Mortality 

 A pplied. of eggs . 



Dec. 15. .... 30 per cent. 

 Jan. 6-22 . . . 42 ,, 



Feb. 18-25 99 . 



whilst in another series (VIII, 54) an application in December 

 proved less satisfactory than applications on January 31 or 

 March 15. No damage attending its use has been noticed, even 

 when the spraying was deferred till the end of March, except in 

 the case of some gooseberries, which were then in leaf, and no 

 permanent injury was caused even to them. It has also been 

 used without bad effect on peaches and nectarines, when the 

 buds were almost bursting. 



Various other substances were examined for destroying mussel 

 scale, without any indications being obtained that they would 



