134 THE SENSE ORGANS AND REFLEX BEHAVIOUR 



this construction were such that a Petri dish j), 15 cm. in diameter 

 and 1 cm. deep, could just be passed beneath the screen without 

 coming in contact with it. Within the Petri dish were mounted 

 two tin receptacles (a and h), 4 cm. long, 2 cm. wide, and of such 

 a height that their upper edges were on a level with the rim of the 

 Petri dish. Two rectangular openings were cut in the screen, so 

 that when the Petri dish was in position they were directly over 

 the tin receptacles. Owing to the fact that the insects in question 

 are well known to feed upon the juices of fallen or decayed fruit, 

 apple juice was used in the experiments and poured into the Petri 

 dish. Two packs of cheese cloth were folded to fit the pans : 

 one was saturated with apple juice (in a), and the other with 

 distilled w^ater (in h). An individual butterfly was held by a 

 specially devised arrangement which gripped the closed wings, 

 and was tested in the apparatus in three positions. In the first 

 position (Fig. 58, B) it was placed as near as possible to the edge of 

 the receptacle a with the antennic reaching out over the cloth 

 saturated with apple juice, but with the four walking legs upon 

 the screen. In the second position the insect was placed in relation 

 to receptacle h, so that the middle tarsi w ere in contact with the 

 distilled water : in the third position the same experiment was 

 performed in relation to receptacle a. 



The conditions of chemical stimulation in the three positions 

 may be summarised as follows : — 



Position 1. Distance stimuli from apple juice. 



Position 2. Distance stimuli from apple juice in the surrounding 

 Petri dish plus contact stimulus of distilled water on the 

 tarsi. 



Position 3. Distance and contact stimuli from apple juice. 



The experiments were carried out with starved individuals, and 

 the response was judged by the coiling and uncoiling of the 

 proboscis. The maximum duration of each trial was one minute, 

 and if no visible uncoiling of the proboscis occurred during that 

 interval " no response " was recorded. With Pyrameis 29 per 

 cent, of the individuals responded in position 1, only 17 per cent, 

 in position 2, and 100 per cent, in position 3. After removal of 

 the antenna?, palpi and vestigial fore legs the experiments were 



