60 SOME SOI Ml INDIAN INSECTS, ETC [CHAP. VII. 



seeming to prefer the drops ol gum exuded by the tentacles, another 

 allied caterpillar attacks the Boerhavia, feeding especially on the 

 droplet ol gum, and the receptacle of the Pitcher-plant supports 

 quit a small fauna of aquatic insects. 



rhe successful fertilisation oi flowers is secured in very various 

 ways, but as a rule plants have developed contrivances by which 

 fertilisation ol the ovaries is accomplished by means "I pollen deri- 

 \ ed from another plain of the same species or, in other words, cross- 

 fertilisation is secured as far as possible. In some cases this end 

 is attained by means ol the wind which carries innumerable grains 

 of pollen of which some few are blown indiscriminately onto the 

 female organs of the same or another plant. But, in the case ol 

 practically all our more fa mi la r flowers, cross-fertilisation is se< an d 

 by utilizing the services of insects and it is supposed, generally 

 -peaking, that the shapes, colours and perfumes of llowers have been 

 elaborated to their present perfection larg"ly as a result of the com- 

 petition between them to attract the \ i-it- of insect-. A- i- usually 

 the case, competition and specialisation have proceeded hand in 

 hand and, whilst some llowers have elaborated gaudy colours to 

 attrai I insects In sight, others have specialized in the development 

 of perfume to tempt the sense of smell of their welcome visitor- ; 

 and it is for this reason that we tind so many handsome flowers 

 without perfume and so many llowers which smell sweetlj but are 

 otherwise' inconspicuous. And specialisation has proceeded further 

 than in the mere development of general attractiveness by parti- 

 cular methods, for many flowers have specialized in the attraction 

 ol certain particular classes ol insects; of such cases that of the 

 Humble-bee and Clover is a familiar instance. And most observers 

 will have noticed that those flowers which exude their perfume 

 towards nightfall usually have white petals which are conspicuous 

 at dusk, at which time such llowers are visited In Haw k-moths and 

 similar insects which only tl> alter sunset. 



On the other hand many insects are highly specialized bj 

 possessing habits or structural modifications which enable them to 

 obtain the nectar offered by the llowers which at the same tun. 

 the} pollinate unconsciously but in the most effective manner. 

 The development of an especially long tongue, such as is found 

 in the Honey-bees and Hawk-moths, may be cited as an example 

 of this, main crepusculai Hawk-moths having a tongue which is 

 much longer than their whole bodies. 



In normal eases the insect, whilst taking the nectar from a 

 Sower, touches the anthers and carries away pollen-grains which 

 it brings into contact with the stigma ol the next llower visited, 



