EXPEKIMENTS WITH COLOURED GLASSES. 193 



red and green, on the contrary, very transparent, and 

 the yellow even more so. The yellow was not darker 

 than a tincture of saffron. The latter indeed, to my 

 eye, scarcely seemed to render the insects under them 

 at all less apparent ; while under the violet and purple 

 I could not trace them at all. I altered the relative 

 positions as before. The nest contained about 50 

 larvae and pupae. 



I made thirteen trials, and in every case the larvae 

 and pupae were brought under the yellow or the green 

 — never once under any of the other colours. 



Again, over a nest of Formica fusca containing 

 about 20 pupae I placed violet glass, purple glass, a 

 weak solution of fuchsine (carmine), the same of 

 chloride of copper (green), and of bichromate of potash 

 (yellow, not darker than saffron). 



I made eleven trials, and again, in every ease the 

 pupae were brought under the yellow or the green. 



I then tried a nest of Lasius fiavus with the 

 pm-ple glass, violet glass, very weak bichromate of 

 potash, and chloride of copper as before. 



With this species, again, the results were the same 

 as in the previous cases. 



In all these experiments, therefore, the violet and 

 purple light affected the ants much more strongly than 

 the yellow and green. 



It is ciurious that the coloured glasses appear to 

 act on the ants (speaking roughly) as they would, or, 



