BISULPHIDE OF CARBON. 211 
from the previous experiments that the bisulphide 
darkened the nests to the ants more than violet glass, 
it would appear to do so less than red, green, or yellow. 
I now made some experiments in order, if possible, 
to determine whether the reason why the auts avoided 
the violet glass was because they disliked the colour 
violet, or whether it was because the violet glass trans- 
mitted more of the ultra-violet rays. 
For this purpose I placed a layer of the bisulphide 
of carbon over a piece of violet glass. By this arrange- 
ment I got the violet without the ultra-violet rays ; 
and I then contrasted this combination with other 
coloured media. 
First, I took a solution of bichromate of potash 
(bright orange), and placed it on a part of the nest, side 
by side with the violet glass and bisulphide of carbon. 
I should add that the bichromate of potash also cuts off 
the ultra-violet rays. In all the following observations 
I changed the position after each observation. 
At 1.30 p.m. the ants were under the bichromate. 
3 3 a half under the bichromate 
and half under the violet 
glass and bisulphide. 
8 AM.,, ‘a under the bichromate. 
8.30 ra 3 under the violet glass and 
bisulphide. 
9 8 5 half under each. 
9.30 ‘s 2 some under each, but most 
