8 



contain more than forty per cent. It is associated chiefly with lime and colouring matter. 

 The arsenic present is in a very tine state of division, and intimately mixed with the lime 

 and other ingredients, forming a very fine powder. It is much more soluble than Paris 

 Green, and hence more liable to scorch the foliage, while its very variable strength makes 

 it uncertain in its effects. For these reasons London Purple is not likely to take the 

 place of Paris Green as an insecticide, which, when unadulterated, is nearly uniform in 

 its composition and effects. An artificial mixture of arsenic and lime of uniform strength 

 and coloured could be supplied at about the same price, and would be more reliable than 

 London Purple ; but, owing to the more ready solubility of the arsenic in this form and 

 its caustic character, it is apt, unless used with much care, to destroy portions of the 

 tissues of the leaves on the plants to which it is applied, making them appear as if 

 scorched or burnt. 



Experiments have been carried on for the past two seasons at the Agricultural Col- 

 lege at Lansing, Michigan, by Prof. A. J. Cook, on the use of London Purple as a remedy 

 for the Codling Worm. Early in the summer, while the fruit was quite small, some crab 

 4\pple trees were syringed thoroughly with London Purple mixed with water, and it is 

 claimed that the poison, which, when the water has evaporated, forms a thin coating on 

 the fruit, either prevents the Codling Moth from depositing her eggs or else poisons the 

 young larvse as soon as they are hatched, the result being the saving of a very large pro- 

 portion of the crop from injury, while other trees near by not similarly treated bore very 

 wormy fruit. It is also said that, as the fruit approaches maturity, the most delicate 

 chemical tests fail to show a trace of the poison. I scarcely think that the experiments 

 yet tried in this direction have been sufliciently extended to warrant any general conclu- 

 sions being based on them ; and provided it were proven that this remedy was a certain 

 and safe one, the popular prejudice against applying such virulent poisons directly to the 

 fruit we are to eat would be so strong as to prevent the general use of any such means. 

 Indeed, were it generally known that the apple growers of any district were in the habit 

 ■of applying arsenic in any form directly to their fruit, it would interfere very seriously 

 with their sales, and it is doubtful if apples so treated would find a ready market any- 

 where. 



It is well known that the seeds of certain noxious weeds will sometimes lie dormant 

 in the soil for almost any number of years, awaiting a favourable opportunity for germi- 

 nating ; but it is not so generally known that the development of insect life is sometimes 

 similarly retarded. It has many times been observed that a few individuals out of a 

 large brood of moths will remain in the chrysalis state over one season and produce the 

 perfect insect the following year, thus remaining a full year more in the dormant condi- 

 tion than is usual ; and instances are on record where the perfect insects have escaped 

 after three years spent in this condition of torpor. Recently, Prof. Piley, of Washington, 

 has called attention to a very remarkable case of retarded development in the eggs of the 

 destructive Pocky Mountain Locust, Caloptenus spretus. These eggs were laid in 1876, 

 on the grounds of the Agricultural College at Manhattan, Kansas. While grading the 

 ground around the chemical laboratory in the autumn, a quantity of eggs were buried 

 some ten inches below the surface, the covering material being clay, old mortar, and bits 

 of stone, and above this a plank sidewalk. On removing and regrading the soil last 

 spring a number of these eggs were disinterred quite sound and fresh-looking, and when 

 exposed to normal influences they readily hatched ; so that these locusts' eggs actually 

 remained nearly four years and a half in the ground unhatched, or four years longer than 

 is their wont. How much longer they would have retained their vitality under favour- 

 able conditions of temperature and dryness is unknown. This point has a very practical 

 bearing and deserves further investigation, not only in reference to the eggs of this insect, 

 but to those of all injurious species whose eggs are deposited on or under the ground. 



The Sub-section of Entomology of the American Association for the Advancemenc of 

 Science met this year at Cincinnati, Ohio, where I had the honour of representing our 

 Society. A large number of distinguished Entomologists were present, and many useful 

 papers read and discussions held at the meetings. An account of the proceedings will 

 appear in our Annual Peport. It having been decided to hold the next meeting of tlie 

 American Association in Montreal, I trust that our representative men in all depart- 



