190 EXPERIMENTS WITH COLOURED GLASSES. 
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. 
Lasius flavus also showed a marked avoidance of 
the violet glass. 
I then experimented in the same way with a nest 
of Formica fusca, in which there were some pup, 
which were generally collected in 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 preceding order, but, as 
before, their place over the nest was changed after 
every observation. 
To our eyes the purple was almost black, the violet 
and dark green very dark and quite opaque ; the pupe 
could be dimly seen through the red, rather more 
clearly through the dark yellow and light green, while 
the light yellow were almost transparent. There were 
about 50 pupze, and the light was the ordinary diffused 
daylight of summer. 
These observations showed a marked preference for 
the greens and yellows. The pupe were 64 times 
under dark green, 3 under dark yellow, 34 under red, 
and once each under light yellow and light green, the 
violet and purple being altogether neglected. 
I now tried the same ants under the same colours, 
but in the sun; and placed a shallow dish containing 
some 10 per cent. solution of alum sometimes over 
