116 A BOOK OF INSECTS 



which we can only guess. The abortive hind-wings, or 

 halteres, of Diptera are very mysterious. They are 

 abundantly supplied with nerves, and it is significant that 

 their loss entails upon the insect an inability to maintain 

 its equilibrium in the air. It may be, therefore, that these 

 organs minister to a " sense of balance." Again, insects 

 are extremely responsive to slight variations of wind, tem- 

 perature, moisture, and atmospheric pressure, while many 

 blind insects can distinguish between light and darkness. 

 The possibility of hearing light must not be overlooked. 

 Quite recently an instrument has been invented by Mr. 

 Fournier D'Albe, of Birmingham University, whereby 

 light is rendered audible to the human ear ; and it is not 

 unreasonable to suppose that insects may be keenly con- 

 scious of ether waves to which our grosser senses fail to 

 respond. 



The case for these hypothetical senses of insects has 

 never been more forcibly put than by Lord Avebury, 

 who, as the result of ingenious experiments, became 

 convinced that ants can see the ultra-violet rays which 

 are invisible to our eyes. " Now, as every ray of 

 homogeneous light which we can perceive at all, appears 

 to us as a distinct colour, it becomes 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 different from 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 additional 

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

 are pure, 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 the rays 

 we see, but of these and the ultra-violet, it would appear 



