smell — fieldwork and experiments 97 



Insects 



In insects, the organs or parts of the body capable of per- 

 ceiving scent are diverse and curious. Many kinds of male 

 moths detect the scent of females with their antennae, but 

 both sexes use these organs in seeking flower nectar on which 

 they feed. This is fairly obvious in night-flying species, when 

 the colour of the flower is no guide. However, the antennae 

 are not the only parts of an insect's anatomy which can detect 

 scents : the palps can do so, and also the specialized hairs on 

 the feet of some flies. 



With the aid of a strong electric torch, it is simple to 

 observe some night-flying moths visiting the flowers of 

 tobacco plants, valerian, stocks, and so on. The Elephant 

 Hawk Moths are suitable species. The moths will be seen 

 flying around the flower-beds, every now and then hovering 

 before a particular bloom or flower cluster; then the moth 

 will drop nearer, almost touching the flower. With care in 

 the use of the torch, the long tube-like proboscis can just be 

 seen as it is inserted into the flower to suck up the nectar to 

 which the moth has been attracted by the scent emanating 

 from it. 



If carefully collected, live specimens of moths can be 

 liberated into a large cage previously provided with some 

 suitable flowers among which are placed a number of well- 

 made artificial flowers in imitation of the live ones. If the 

 live blooms are very lightly sprayed with water an hour or 

 so before the experiment is carried out and the room is 

 warm, the moths will often fly ; and it will be seen that the 

 artificial flowers are approached, but no attempt will be 

 made to feed from them. The moths will then try another 

 bloom where there is a supply of sweet-smelling nectar. 



It is also possible to train butterflies to take in sugar-water, 

 and this kind of test can demonstrate taste as well as smell 

 if a drop of perfume, to match the natural scent of a flower 

 known to be favoured by the butterfly in question, is mixed 

 with the sugar-water. If two dishes are used for the feeding 

 liquor and one is scented and the other is not, the butter- 

 flies will tend to feed more readily from the dish which is 

 perfumed. 



