1919.] The Sixth Indian Science Conaress. exliii 
Now you know that with ourselves any stimulus, such as 
a smell, a light or a colour, a sound, a touch, or a taste, has 
) e above e 
height if it is to pass the threshold of our consciousness, and 
the height of the threshold varies in different people and at 
different times. The lower the threshold, the more delicate 
the perception. 
So instead of plotting the beetle’s attractiveness we will 
represent the variations in the height of his sensory threshold 
for the smell of the flowers on which he feeds. 
ust as the seed of the flower had no attraction, so we 
may or it that the beetle has no perception . flower-smell 
when he is an egg, or even when he is a grub or upa; he is 
to pass a very high threshold before they can penetrate to his 
consciousness. 
But the height of the threshold will drop abruptly when 
he enters the final winged stage of his existence, wherein he 
depends on the flowers for food. Two things will then chiefly 
interest him—finding his proper aes and finding a mate: 
but if we omit the complications associated with the latter 
pursuit, we can represent the va eee of his flower-smel! thres- 
hold by a curve like this. (Fig. 5 
Threshold. 
ij T T a 
Eco Larva Pepa imaco Eco 
Fre. 5. 
shows the intensity of the — that he is able to 
ihe at different periods of his ca is attention will 
“i be engaged by any smell whose iribeainity “alls below the 
lin 
i will see that this means that the beetle cannot make 
elléetivs, contact age his range of mobility extends at least 
to this —_— (Pl. I, fig. 
Then it will be te. that if this point is a little beyond the 
average mobility of this kind of beetle, only exceptionally 
