Kirk. — On Mosquito Larviddes. 



195 



In the column " Dead " is noted the time at which removal to abundant 

 fresh water was made in cases where this removal did not bring about at 

 least temporary recovery. For this purpose I regarded proof of death as 

 sufficient if no movement of any kind took place within twenty-four hours. 



No very young larvae were used in these experiments. 



Emulsion. 



Strength. 



a s 



Time. 



Larvae observed to be 



Active. Twitching. 



Apparently 

 Dead. 



Dead. 



Remarks. 



Carbolic 



>? 

 Cresolia 

 Light oil 



Recover in fresh water. 

 One recovers in fresh water. 



Dead in 40 minutes. 



Dead in 2 hours 30 minutes. 



Dead in 2 minutes. 



Dead in 40 minutes. 



No observation between 

 3 p.m. and 7 p.m. Dead 

 within 4 hours 10 minutes. 



No observation between 

 7 p.m. and 2.52 p.m. next 

 dav. Dead within 24 hrs. 



* One of these was a pupa. 



Many other substances, including well-known disinfectants and plant- 

 sprays, were used, but with no results worth publishing. Sulphates of 

 iron and of copper, potassium ferrocyanide, and other well-known sub- 

 stances gave, in the dilution of 1 in 4,000, negligible results. 



From the above table it will be seen that when there is no access 

 of fresh water an emulsion of light oil may be used in the proportion of 

 1 in 32,000. The emulsion that will give this result must, of course, be one 

 that contains nearly all the light oil that the emulsionizing agent can carry 

 and that has no needless water. The formulae here given, chosen from a 

 number that have been arrived at, may be relied upon : — 



(1.) Soft-soap .. .. .. .. .. 100 parts. 



Light oil . . . . . . . . . . 440 „ 



Water .. .. .. .. . . 100 „ 



Caustic soda . . . . . . . . 80 ,, 



It is best to add the light oil after the other substances have been heated 

 together to a temperature of 100° C. 



This is a thick jelly, and may be diluted with water to liquefy it. 



(2.) Soft-soap . . . . . . . . 20 parts. 



Light oil . . . . . . . . 50 ,, 



A thick jelly-like soap. 



Where transport was not an important consideration the desired amount 

 of water to make these emulsions liquid would usually be added when they 

 were being made. 



(3.) Castor-oil . . . . . . . . 50 parts. 



Caustic soda (sat. solution of 98 per cent, caustic 



soda) . . . . . . . . 15 ,, 



Water . . . . . . . . . . 20 „ 



Light oil . . . . . . . . . . 170 „ 



7* 



