iv.] EXPERIMENTS WITH COLOURED LIGHTS. 133 



I then allowed some ants (Lasius niger) to find some 

 larvse, to which they obtained access over a narrow paper 

 bridge. When they had got used to it, I arranged so 

 that it passed through a dark box, and threw on it the 

 principal colours of the spectrum — namely, red, yellow, 

 green, blue, and violet, as well as the ultra-red and ultra- 

 violet ; but the ants took no notice. 



At the suggestion of Prof. Stokes, I then tried the 

 following experiments. Mr. Spottiswoode not only most 

 kindly placed the rich resources of his laboratory at my 

 disposal, but he and his able assistant Mr. Ward were 

 good enough to arrange the apparatus for me. 



We tried the ants (Formica cinerea, Lasius niger, and 

 Myrmica ruginodis) with coloured lights in a Bunsen's 

 burner, using chloride of strontium and carbonate of 

 lithia for red, chloride of barium for green, and chloride 

 of sodium for yellow. The lithium gives an almost pure 

 red, the strontium and barium give a little yellow, but 

 so little that I do not think it would affect the ants. 



The yellow of the soda-flame certainly affected the 

 Formica cinerea, but the others seemed to take no 

 notice of it. 



The barium also affected the F. cinerea, but neither 

 of the others ; I could not feel sure whether it was the 

 green or the accompanying yellow which disturbed them. 

 The red of the lithium was not so brilliant, still the F. 

 cinerea seemed to perceive it. 



The strontium-flame did not seem to have any effect 

 on the ants. 



It is obvious that these facts suggest a number of 

 interesting inferences. I must, however, repeat the 

 observations, and make others ; but we may at least, I 



