102 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



KC1 (and NH 4 C1), all, except LiCl, appeared to have very 

 little toxicity, the exceptional behaviour of LiCl being what 

 was expected. It should be mentioned that as some of the 

 chlorides were insoluble in water, attention had to be con- 

 fined only to those chlorides that entered into true solution 

 with water, and for the study of toxicity equimolecular 

 solutions of the salts were always taken. 



' (2) Experiments were continued on the correspondence 

 of the toxicity of volatile organic compounds to their boiling 

 points. Cotton plugs thoroughly soaked in the chemicals, 

 were allowed to remain for 48 hours in small phials con- 

 taining a thin layer of water, care being taken not to bring 

 the plug in contact with the water. Three larvae of 

 Stegomyia scutellaris were then introduced in each of the 

 phials and the time when they died noted. The data so far 

 obtained are scanty and do not warrant a definite 

 conclusion. 



" (3) Observations were continued on the comparative 

 behaviour of larvae and pupae of mosquitos towards soluble 

 and insoluble salts and poisons. Whereas mosquito larvae 

 . are generally readily killed by minute quantities of HgCl 

 sprinkled in water, the pupae have almost always been found 

 to resist the action of the salt and to turn into adults. The 

 same was observed with other halogen salts of mercury 

 which were insoluble in water and also some of the insoluble 

 alkaloids. The results obtained seemed to confirm the pre- 

 vious conclusion that the soluble substances operate chiefly 

 cutaneously and the insoluble substances orally (' Effect of 

 mercurous chloride on mosquito larvae,' read before the Sixth 

 Science Congress). 



" (4) In connexion with the Imperial Pathological 

 Entomologist's work on ' Culicifuges ' a series of concurrent 

 observations was carried out on the deterrent effects of the 

 following chemicals on Chcetodacus zonatus with a view to 

 finding out any analogy between the chemotactic reaction 

 of fruit flies and that of mosquitos. The experiment con- 

 sisted in dissolving varying quantities of methyl eugenol 



