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 

 purple looked almost black, the violet very dark ; the 



