ANIMAL FLIGHT I3I 



as a stick, fence post, plant or stone, and release a fine thread 

 or several of them, or sometimes a tangled mass of threads. 

 When the pull of the ascending air upon the threads is strong 

 enough the spider lets go his hold and floats away. One of 

 the most sedentary of the spiders, living as a rule under stones, 

 sticks and other objects, has adopted this means of getting from 

 place to place, and it is also used by spiders of many other 

 kinds. Occasionally spiders try to rise in an adverse wind, and 

 then their threads instead of rising are blown onto the ground 

 or onto the nearby plants sometimes forming enormous sheets 

 of silk. These sheets of silk may later be lifted up and blown 

 away, coming down in some distant place as a so-called gossa- 

 mer shower. 



Many insects, especially the smaller ones like aphids, can 

 fly just well enough to keep up in the air without making 

 much of any progress. These form a connecting link between 

 creatures that fly by their own efforts and those that are 

 wafted by the winds from place to place. 



Many caterpillars, such as those of the g>T>sy moth, are, 

 when very small, widely distributed by the strong winds of 

 spring. 



When a pond dries up many of the small water creatures 

 either condense themselves into the smallest possible space and 

 surround themselves with a tough shell, or form highly resistant 

 eggs and die. These capsules and eggs 'are picked up by the 

 wind and carried for long distances; in fact the air, even for 

 hundreds of miles at sea, always contains besides mineral dust, 

 particles representing the remains and the living spores and 

 seeds of animals and plants. This is why any puddle of water, 

 no matter where it is, on the ground, on a roof, or in hollows 

 in the branches of tall trees, swarms with life almost immedi- 

 ately after its appearance. 



Among the animals on land which do not fly, many of the 

 larger ones have certain adaptations which enable them to use 

 the resistance of the air for their protection. Leaping animals 

 that live in tree tops, like the lemurs and the smaller monkeys 



