NOTES ON A COLOUR TROPISM OF ASTEROCHITON VAPORARIORUM, VVESTW. 357 



Experiment 12. 



December 20th-23rd ; little weak sunlight ; 32 hours' daylight. Three strengths of 

 orano-e G., -,}-, ~\^, -^^ pe^" cent., four tubes of each ; 849 flies were trapped as follows : 

 1 per cent.!'257flieM30 per cent.) ; ^i^ per cent., 274 flies (32 per cent.) ; ^i^ per 

 cent. 518 flies (37 per cent.). This is not a decisive result, although the figures appear 

 to be graded, the differences being within the range of experimental error and rather 

 erratic in the separate counts. 



The solution which drew forth the greatest response was thus one of orange G., 

 of a strength approximatirig to y|i^ per cent. 



i^ 25 



«>^ 15 - 



5 I 1/4. Vi6 '/64 ''256 



Percent3c/e stren^t/} of so/c/t/'or) 



Diagram 2. (See Experiment 9.) 



Va Vis Viae /biz ] 



'A Me '/64 '/256 t^^-^^S'i^^ 



£osin CSro/fe/y //he-) J 



'/e% ^otassiom 6/c^'~omate 

 cont/'o/ /'(/n-'ite</ //hej 



Diagram 3. (See Experiment 10.) 



Experiments with Reflected Light. 



Experiment 3. 



December 2nd ; a strip of white card, seven inches long and one and a half inches 

 broad, was divided by transverse lines into seven equal sections, and these were 

 painted with water-colour washes in the following order : red, orange, yellow, grefcn, 

 blue, indigo, violet. Wlien dry this was lightly smeared with a transparent adhesive 

 and placed horizontally in the cage one foot above the bottom of the well, which 

 contained infested foliage. The flies left the foliage and flew to the top of the cage, 

 and were then in a position to see the trap. The card was exposed for two hours, 

 the sun being bright. At the end of the first hour the card was turned, to reverse 

 the position of the colours. In all, 397 flies were trapped, and their distribution is 

 shown in diagram 4. Orange, green and yellow proved attractive, the last-named 

 trapping 51 per cent, of the total. The four remaining colours held only about 

 10 per cent, of the total catch. 



Experiment 11. 



December 19th-20th ; a small tomato leaf one and a half inches long was taken, 

 and six pieces of paper of the same size and shape were washed with water-colours 

 as follows : red, orange, yellow, yellowish -green, blue and white. Each of these 

 (4183) 2 c 



