EXPERIMENTS WITH COLOURED GLASSES. 191 



the yellow, sometimes over the red. I also put four 

 thicknesses of violet glass, so that it looked almost 

 black. 



Under these circumstances, the pupae were placed 

 under the red 7 times, dark yellow 5, once they 

 were half under each, but never under the violet, 

 purple, light yellow, dark or light green. 



The following day I placed over the eame nest, in 

 the sun, dark green glass, dark red, and dark yellow. 

 In nine observations the pupae were carried three times 

 under the red and nine times under the yellow. 



I then tried a similar series of experiments with 

 Lasius niger, using a nest in which were about 

 40 pupae, which were generally collected in a single 

 heap all together. As before, the glasses were moved 

 in regular order after each exj^)eriment ; and I arranged 

 them so that the violet followed the red. As far, 

 therefore, as position was concerned, this gave violet 

 rather the best place. The glasses used were dark 

 violet, dark red, dark green, and yellow, the yellow 

 being distinctly the most transparent to our eyes. 

 Experiment Experiment 



