E. R. Speyer 137 



citronella oil, and cedar oil for lemon oil, bears this out. Flies were still 

 abundant round the traps. 



Experiment 15. Repulsion by essential oils. 



Date:— September 26th-28th. 



General weather conditions: — Cool, bright. 



Duration of experiment: — 42 hours. 



It must be remembered that these figures are comparable to the 

 first two periods of Exp. 14, and orange oil holds the same place in both 

 cases. 



The latter oil appears to lose its repellent power sooner than lemon 

 oil and citronella oil. 



Experiment 16. Repulsion by essential oils. 



Date:^September 25th-26th. 



General weather conditions :— Cool, bright. 



Duration of experiment :— 27 hours. 



'{ 



None of these can be truly repellent except camphor oil, and traps 

 set alone with oil of bitter almonds, a substance with a smell resembling 

 benzaldehyde, show that the latter is certainly not attractive. The same 

 has also been demonstrated with cedar oil and eucalyptus oil. The high 

 figures for camphor oil were no doubt due to the enormous numbers of 

 flies round the traps, and another experiment was made to certify 

 this. 



