IMPERIAL BUREAU OF ENTOMOLOGY. 



REVIEW 



OF 



APPLIED ENTOMOLOGY 



* * Series B. 



Vol. VII.] [1919. 



Kirk (H. B.). On Mosquito Larvicides. — Trans. & Proc. New 

 Zealand Inst, for 1917, Wellington, \, 15th July 1918, pp. 193-196. 



The control of mosquito larvae is usually efiected either by means 

 of a film that prevents their breathing when they come to the surface, 

 or by the use of a letlial agent that diffuses evenly throughout the 

 water. The substances generally used are crude petroleum for the 

 former and an emulsion of crude carbolic acid for the latter. 



Light oil, which comprises those constituents of coal-tar distillate 

 that have a boiling-point up to 392° or 410° F., is very fatal to fly 

 larvae or to adult flies when sprayed in mixture or in emulsion with 

 3 or 4 parts of water. It has to be applied in greater strength to kill 

 the pupae. 



Experiments with the larvae of various species of Culex found in 

 New Zealand, and with the larvae of a Culicine mosquito often found in 

 brackish water on the coast near Wellington, have shown that light 

 oil is most useful as a mosquito larvicide, whether used as a film" 

 or as an emulsion. It makes a film that spreads more rapidly than 

 crude petroleum ; its colour enables the operator to see at a glance 

 whether the film is complete ; it is very fatal to insects, and a larva 

 thrusting the breathing-siphon into the film is paralysed and seldom 

 comes again to the surface. Experiments with dishes of the same size, 

 containing equal quantities of water and the same number of larvae 

 at the same stage, and treated with light oil and crude petroleum 

 respectively, have shown that the larvae in the former case have all 

 been dead, or helpless on the bottom within fifteen minutes, while 

 those under the crude petroleum have been ahve and active after 

 an hour or more. In view of the possible Ifteaking of the film by 

 wind, comparative rapidity of action is a matter of great importance. 



The film is best produced by spraying, but the oil may be sprinkled 

 from a bottle or other vessel, or a leafy twig may be dipped in it and 

 shaken over the water. A spraying instrument should be chosen 

 with(j|it rubber tubing, as some constituents of light oil are solvents 

 of rubber. 



(C530) Wt. P2/137. 1,500. 1.19. B.&F.Ltd. Gp.11/3. a 



