188 EXPERIMENTS WITH COLOURED GLASSES. 
I then (July 15, 1876) laid the strips of g'ass on 
one of my nests of Formica fusca, containing about 
170 ants. These ants, as I knew by many previous 
observations, seek darkness, at least when in the nest, 
and would collect in the darkest part. I then, after 
counting the ants under each strip, moved the glasses, 
at intervals of about half an hour, so that each should 
by turns cover the same portion of the nest. The 
results were as follows—the numbers indicating the 
approximate numbers of ants under each glass (there 
were sometimes a few not under any of the strips of 
glass) :— 
1. Green. Yellow. Red. Violet. 
50 40 80 0 
2. Violet. Green. Yellow. Red. 
0 20 40 100 
3. Red. Violet. Green. Yellow. 
60 0 50 50 
4, Yellow. Red. Violet. Green. 
50 70 1 40 
5. Green. Yellow. Red. Violet. 
30 30 100 0 
6. Violet. Green. Yellow. Red. 
0 14 5 140 
7. Red. Violet. Green. Yellow 
50 0 40 70 
8. Yellow. Red. Violet. Green. 
40 50 1 70 
