INSECTS. 109 



the creatures make themselves appear to be a part 

 of the stem upon which they alight. The insect 

 known as the "walking-stick" so resembles a dead 

 brown twig that it would be taken for such when 

 at rest on a tree or shrub. Some night-flying 

 moths sleep during the day attached to the trunks 

 of trees, and so fold their wings as almost com- 

 pletely to resemble the bark of the tree upon 

 which they rest, and thus avoid being picked up by 

 birds. 



Devices for mimicry are almost as numerous as 

 the different forms of insect life. Mimicry, how- 

 ever, is not confined to insects alone, but is com- 

 mon to all classes of animals. It is thought that 

 the stripes of the tiger are there to make it har- 

 monize with the large grass blades among which it 

 lurks. In this case, perhaps, the resemblance is 

 not to conceal the tiger from danger, but that his 

 prey will approach near without seeing him. 



Scientists have found that most plants do better 

 when the pollen of one falls upon the blossom of 

 another of the same Jkind than when the pollen 

 falls upon the same blossom that produced it. The 

 offspring of such a plant does better than others 

 because it partakes of the qualities of two parents 

 instead of those of one. A weakness in one par- 

 ent may be compensated by corresponding strength 

 in the other. This method of pollination is called 

 cross-fertilization. Plants in which the pollen falls 

 upon the. blossom that produced it soon become 



