162 THE ENTOMOLOGIST. 



an inch, a distance which leaves just room enough for the ants to 

 move about freely. He found that if he covered over part of the 

 glass with any opaque substance, the young were always carried 

 into the part thus darkened. He then tried placing over the nest 

 different coloured glasess, and found that if he placed side by 

 side a pale yellow glass and one of deep violet, the young were 

 always carried under the former, showing that though the light 

 yellow was much more transparent to our eyes, it was, on the 

 contrary, much less so to the ants. So far he had gone in 

 experiments already recorded. But he now wished, as already 

 mentioned, to go further, and test the effect upon them of the ultra- 

 violet rays, which to us are invisible. For this purpose, among 

 other experiments, he used a solution of sulphate of quinine and 

 bisulphide of carbon, both of which transmit all the visible rays, 

 and are therefore perfectly colourless and transparent to us, but 

 which completely stop the ultra-violet rays. Over a part of one 

 of his nests he placed flat-sided bottles containing the above- 

 mentioned fluids, and over another part a piece of dark violet 

 glass ; in every case the larvae were carried under the transparent 

 liquids, and not under the violet glass. Again, he threw a 

 spectrum into a similar nest, and found that if the ants had to 

 choose between placing their young in the ultra-violet rays or in 

 the red, they preferred the latter. He infers, therefore, that the 

 ants perceive the ultra-violet rays, which to our eyes are quite 

 invisible. Now as every ray of homogeneous light which we can 

 perceive at all appears to us a distinct colour, it seems probable 

 that these ultra-violet rays must make themselves apparent to the 

 ants as a distinct and separate colour (of which we can form no 

 idea), but as unlike the rest as red is from yellow, or green from 

 violet. The question also arises whether white light to these 

 insects would differ from our white light in containing this ad- 

 ditional colour. At any rate, as few of the colours in nature are 

 pure colours, but almost all arise from the combination of rays of 

 different wave-lengths, and as in such cases the visible resultant 

 would be composed not only of tlie rays which we see, but of 

 these and the ultra-violet it would appear that the colours of 

 objects and the general aspect of nature must present to them a 

 very difterent appearance from what it does to us. Similar ex- 

 periments which Sir John also made with some of the lower 

 Crustacea j)oints to the same conclusion, but the account of these 



