138 Notes on Cliemotropism in the House- Fly 



Experiment 17. Repulsion by essential oils. 



Date :— September 28th-30th. 



General weather conditions : — Bright, cool. 



Total duration of experiment : — 45 hours. 



Flies caught 



Amount at Amount at Period 1, 22 hours Period 2, 23 hours 



Substance start finish , * , / . 



cc. $ $ Total 3 Total 



Camphor oil 14 1 cc. ] 



Grape juice 20 renewed at J- 1 1 1 1 



each periodj 

 Cedar oil 14 13 cc. "| 



Grape juice 20 renewed at f 1 4 5 7 1 8 



each periodj 

 Oil of Pinus Sylvestris 14 3-5 cc ") 



Grape juice 20 renewed at f 1 1 



each periodj 



The author wishes to make it clear that he does not consider the 

 experiments upon actual repulsion by essential oils in any way final 

 until further observations are made in a similar direction. This applies 

 to eucalyptus and camphor oils, two substances of almost indistinguish- 

 able odour when in the pure state, in special. 



Weather conditions may have much to do in determining the re- 

 pellent qualities when placed in juxtaposition with attractive substances, 

 and when flies are in great numbers, it is not impossible that they should 

 invade, to them malodorous compounds, to reach positively chemotropic 

 reagents. 



The conclusions drawn, then, are subject to revision. 



1. Essential oils are unattractive to the house-fly in general. 



2. Certain essential oils evoke negatively chemotropic stimuli, these 

 being oil of Pinus Sylvestris, orange oil, lemon oil, citronella oil, oil of 

 juniper berries, and possibly camphor oil. 



3. Certain essential oils are inactive in raising stimuli, these being 

 cedar oil, eucalyptus oil, and oil of bitter almonds. They may them- 

 selves be neither positively, nor negatively, chemotropic in action, but 

 probably have slight negative features. 



4. During evaporation, the repellent actions pass off, soonest in 

 orange oil and later in lemon oil, citronella oil, and oil of Pinus Sylvestris, 

 and some coordination may occur in relation to the rate of evaporation 

 and the retention of repellent qualities. 



Note : — Essential oils are not repellent to all insects. Gryllidae were 

 repeatedly found in camphor, lemon, citronella oils; also some Diptera 



