Guests Welcome and Unwelcome 231 



and the butterflies would not rise high enough to find 

 them. 



Under these circumstances, therefore, many trees, 

 such as the custard-apple, bear their blossom on the 

 trunks or larger branches, where moths and butterflies 

 can find them. The cacao is another which does so, 

 and when the large yellow fruit is ripe, the trunks of 

 some of the smaller trees are hardly to be seen, so 

 thickly does it cover them. 



But, much as these insects do both in the tropics 



and in the mountains, it must not 



be supposed that their services could 



be dispensed with even in temperate 



latitudes and in the plains. Quite 



the contrary. Most of the European 



orchids are fertilized by bees, but 



just a few species cannot get on 



without the help of moths. There 



is a large sphinx-moth which carries 



pollen to and from one species of 



orchid in a very curious way on its 



eyes. The pollen of this flower 



grows in two masses, each perched 



upon a stalk which passes through its centre, and to 



which the grains are united. At the base of the stalks 



are tiny button-shaped discs, one on each side of the 



stigma, face to face. When the moth presses its head 



into the centre of the flower, the discs come into 



contact with its eyes, and, being very sticky, they 



adhere so firmly that the whole thing is dragged out 



stalk, pollen, and all. A very strange object one of 



these moths is when it is thus adorned, for the stalks, 



with their lumps of pollen at the end, at first stand out 



