1879.] 



on the Habits of Ants. 



189 



Average, Red over 70, Green 48, Yellow 45, Violet \, 



Adding these numbers together, there were, in the twelve observa- 

 tions, under the red 890, under the green 544, under the yellow 495, 

 and under the violet only 5. The case of the violet glass is most 

 marked. To our eyes the violet was as opaque as the red, more so 

 than the green, and much more so than the yellow, yet, as the 

 numbers show, the ants had scarcely any tendency to congregate 

 under it. There were nearly as many under the same area of the 

 uncovered portion of the nest as under that shaded by the violet 

 glass. 



I also experimented in the same way with a nest of Formica fusca^ 

 in which there were some chrysalises. These chrysalises were 

 generally collected into a single heap. I used glasses coloured dark 

 yellow, dark green, light yellow, light green, red, violet, and dark 

 purple. The colours were always in the same order, but the places 

 were shifted after each observation. To my eye the purple was 

 almost black, the violet and dark green very dark and almost opaque; 

 the j)urple could be dimly seen through the red, rather more clearly 

 through the dark yellow, while the light yellow and light green were 

 almost transparent. The purple were in fifteen observations six times 

 placed under the dark green, three under dark yellow, four under 

 dark red, once each under light yellow and light green, but not once 

 under the violet or purple. In another experiment the purple were 

 placed seven times under the red, six under the dark yellow, never 

 under any of the other colours. The same experiment tried with 

 another species — Lasius niger — gave very similar results ; the purple 

 being placed in forty experiments, nineteen times under the dark 

 yellow, sixteen under the red, five under the green. In some sub- 

 sequent experiments the green and yellow seemed to be decidedly 

 preferred to the red. 



It is curious that the coloured glasses appear to act on the ants 

 (speaking roughly) as they would, or, I should rather say, inversely 

 as they would on a photographic plate. It might even be alleged 

 that the avoidance of the violet glass by the ants was due to the 

 chemical rays which are transmitted. From the habits of these 

 insects such an explanation was very improbable. If, however, the 

 preference for the other coloured glasses to the violet was due to the 

 transmission, and not to the absorption of rays, that is to say, if 

 the ants went under the green and red rather than the violet, because 



