192 EXPERIMENTS WITH COLOURED GLASSES. 



I now put two extra thicknesses of glass over the 

 red and green. 



33. Pupae under red. 



34. „ yellow. 



35. „ red. 



36. „ yellow. 



37. Pupae under red. 



38. „ „ 



39. „ yellow. 



40. „ red. 



The result is very striking, and in accordance with 

 the observations on Formica fusca. In 40 experi- 

 ments the pupae were carried under the yellow 19 

 times, under the red 16 times, and under the green 5 

 times only, while the violet was quite neglected. 

 After the first twenty observations, however, I removed 

 it. 



I then tried a nest of Cremastogaster scutellaris 

 with violet glass, purple glass, and red, yellow, and 

 green solutions, formed respectively with fuchsine, 

 bichromate of potash, and chloride of copper. The 

 pui-ple looked almost black, the violet very dark ; the 



