126 Notes on Chemotropism in the House-Fly 



Exp. 



1 

 2 



3. A different temperature over any one period of time from that 

 of another would have the effect of influencing the number of flies 

 attracted to traps placed in the most favourable positions. 



This error, which could not be rectified, is the only one to be con- 

 sidered, and it is very unlikely that the figures given were affected to 

 anything but a negligible degree. 



Experiment 1. Common food-stuffs. 



Date :— August 27th-29th. 



General weather conditions: — Dull, cool at start. 



Bright, hot at finish. 

 Duration of experiment: — 90 hours. 



Flies caught 



Substance 



Amount 



Control substance 



Flies caught 



$ $ Total 

 \ crushed in dish 456 715 1171* Brown sugar and water 

 30c.c. Ill 229 340f 



Banana 



Vanilla extract in 



61 % alcohol 

 Acetic acid (glacial) 30 c.c. 2 4 6 „ „ 1 10 11 



* Includes 147 q<3 and 204 $$ found dead in traps. 



t Includes 15 ^o an d 17 $$ found dead in trap and 74 flies found dead in liquid. 



Experiment 2. Common food- stuffs. 



Date: — August 31st-September 1st. 

 General weather conditions: — -Bright, hot. 

 Duration of experiment: — Experiment substances, 48 hours. 

 Control substances, 24 hours. 



Exp. 



Substance 



Vanilla extract 



(ordinary) 

 Lemon extract 

 Spirit of vinegar 



Amount 



20 c.c. 



zo c.c. 

 25 c.c. 



Flies caught 



Control 

 substance 



Amount 



Flies caught 



(J 

 17 



2 

 3 



9 Total 

 27 44* 



10 12 



Grape juice 10 c.c. 



10 c.c. 

 10 c.c. 



49 



3 

 22 



? Total 

 55 104 



4 

 51 



7 

 73 



* Including 2 found dead in trap and 3 flies dead in liquid. Five flies found dead in 

 grape juice. Control substances were only used during the second 24 hours of this experi- 

 ment. 



In these experiments the "Amount" given denotes the total quantity 

 of the substance used for the three interpositions: at the end of each 

 interval of time the substances were renewed. 



The figures show that banana is the most attractive substance, 

 grape juice, vanilla extract, lemon extract, brown sugar and water, 

 spirit of vinegar and glacial acetic acid following in order. 



The strong grape juice controls in Exp. 2 attracted the flies away 

 from the vanilla extract and lemon extract: this is shown by the fact 



