GROUPS OF ANIMALS 



267 



an adult butterfly emerges. In moths the pupal stage 

 is passed in a cocoon made of silk or other material. 

 Many insects pass the winter in this quiescent stage. 



Insects are of great interest to man for many rea- 

 sons. 1. Many adaptations occur in insects. 2. Bees 

 and ants are a source of interest because they live in 

 colonies. 3. Many insects are useful to. man: the bee 

 supplies honey and wax; the silk worm, silk; and the 

 lady beetles destroy injurious insects. 4. Much destruc- 

 tion results from the fact that many insects feed upon 

 plants useful to man. 



The spiders differ from the insects in the absence of 

 wings and in the fact that 

 they have four pairs of legs. 

 The nests of spiders are made 

 of a silk-like material formed 

 in the body and fashioned 

 into the characteristic web by 

 the legs. 



Mollusks. The three most 

 common members of this 

 group are the clam, the oyster, 

 and the snail. The bodies of 

 these animals are not segmented and they bear no 

 appendages. They are soft and are protected by a 

 shell. In the clam and the oyster this shell is com- 

 posed of two parts called valves. It is formed by a 

 fold of skin known as the mantle. Over the inside 

 of the shell a thin, pearly substance is formed 



Fig. 124. A spider. 



