INSECTS AND FLOWERS 223 



insects capable of extracting nectar from a given blossom. 

 There are many species of hawk-moths with very long 

 sucking-trunks. Except when the insect is feeding, the 

 trunk is coiled up beneath the head ; but it can be shot 

 out and inserted into a flower with great rapidity and 

 precision. This may be observed by watching the 

 beautiful elephant hawk-moths as they fly on summer 

 evenings about such blossoms as honeysuckle and rhodo- 

 dendron. Some exotic moths have trunks twice, or even 

 thrice, as long as their own bodies. They visit flowers 

 with exceptionally long and narrow tubes, such as those 

 of the Nicotiana or tobacco. This plant is also typical of 

 many which reserve their flowers exclusively for insects 

 that fly in the twilight or at night. In full sunlight the 

 tobacco flowers are all tightly shut up and look half-dead ; 

 but as evening approaches each one unfolds its petals and 

 becomes an alluring star, readily distinguishable at a dis- 

 tance long after the reds and blues and purples of other 

 flowers have faded away in the gloom. 



The fact that most night-blooming plants have pale 

 or white flowers corroborates the view that insects can 

 see and appreciate colours. Moreover, the flowers of cer- 

 tain plants are highly coloured and conspicuous in exact 

 proportion to their dependence upon the visits of insects. 

 A striking case in point is that of our wild crane's-bills. 

 The handsome meadow crane's-bill (Geranium pratense) 

 has purplish-blue flowers which are nearly twice as large 

 as those of the mountain crane's-bill (G. pyrenaicum), 

 which again has much larger flowers than those of the 

 dove's-foot crane's-bill (G. molle) ; while those of G. 

 pusillum, which grows commonly on waste ground, are 

 still smaller. Now the meadow crane's-bill, like the rose- 

 bay willow-herb, is absolutely dependent upon the visits 

 of insects, because the stigma does not mature until all the 



