DISPERSION OF POLLEN BY ANIMALS. 



155 



by their appearance might lead one to think that the flower had faded (see fig. 238). 

 But as evening approaches the wrinkles vanish, the petals unfold, spread themselves 

 out into a star, and become slightly reflexed once more. One peculiarity of these 

 flowers is that the inner surface of the petals is white, whilst the outer surface 

 is always of some inconspicuous colour, such as dirty-yellow, greenish, brown, dull 

 red, or ashen-grey. Hence the radiating petals with their white inner surfaces 

 exposed are very striking in the evening darkness, whereas in the daytime the 

 crumpled petals with only their backs visible are anything but conspicuous, and 

 give the impression of being already brown and withered, as maj"- be seen in fig. 

 238. They are consequently not noticed 

 by insects ih the daytime and receive no 

 vib'ts from them. 



This appears to be exactly what is 

 aimed at. Such insects as visit flowers 

 by day in order to suck their honey 

 would be the reverse of welcome to the 

 Catchfly. The filaments are reflexed, the 

 anthers shrivelled and empty or dropped, 

 and there is no pollen in the flower to be 

 brushed off". A honey - sucking insect 

 could not either take up or deposit pollen 

 in the daytime, and the honey would 

 therefore be sacrificed in vain. Indeed, 

 the flowers would be worse off' inasmuch 

 as, being despoiled of their honey, they 

 would possess one less means of attrac- 

 tion in the ensuing night. On the 

 approach of night the pollen-laden an- 

 thers and velvety stigmas appear in front 

 of the entrance to the interior of the flower where the honey is concealed, the scent 

 and white colour act as allurements, and the visits of insects are welcome, provided 

 the size of their bodies is such that they rub against the pollen or stigmas and fly 

 quickly from one flower to another. Those which are too small, or are destitute of 

 wings, are still kept at a distance, this being eflPected by means of contrivances 

 which will be the subject of discussion later on. Of all the welcome species the 

 best adapted in respect of size and shape of body, length of proboscis, and various 

 other structutal characteristics are the Owlet Moths (Noctuse), and of these in par- 

 ticular those of the genus Dianthoecia, one of which is represented as visiting the 

 flower of the Nottingham Catchfly in fig. 239. These little moths pay frequent 

 visits to suck the honey whilst the females also lay their eggs in the flowers. It 

 sometimes happens, too, that the females become loaded with pollen from a flower 

 upon which they have rested and taken a meal of honey, and that afterwards they 

 fly with the pollen to other flowers where, instead of sucking any more honey, they 



Fig. 239.— The Nottingham Catchfly (Silene nutans) by night; 

 a flower being visited by the moth Dianthoecm alhimacula. 



