EXPERIMENTS WITH COLOURED SOLUTIONS. 195 



In another experiment with Lasius niger I used 

 the dark yellow glass, dark violet glass, and a violet 

 solution of 5 per cent, ammonio-sulphate of copper, 

 diluted so as to be, to my eye, of exactly the same tint 

 as the violet glass ; in 8 observations the pupae were 

 three times under the violet solution, and 5 times 

 imder the yellow glass. I then removed the yellow 

 glass, and in 10 more observations the pupse were 

 always brought under the solution. 



It is interesting that the glass and the solution 

 should affect the ants so differently, because to my 

 eye the two were almost identical in colour. The 

 glass, however, was more transparent than the solu- 

 tion. 



To see whether there would be the same difference 

 between red glass and red solution as between violet 

 glass and violet solution, I then (Aug. 21) put over a 

 nest of Formica fiisca a red glass and a solution of 

 carmine, as nearly as I could make it of the same tint. 

 In 10 experiments, however, the ants were, generally 

 speaking, some under the solution and some under 

 the glass, in, moreover, as nearly as possible equal 

 numbers. 



xiugust 20. — Over a nest of Forviica fusca con- 

 o 2 



