ARTHROPODA. 



203 



somewhat, and begins to secrete another shell. This 

 may be repeated, as in the lobster, six or seven times before 

 it becomes like the adult (Fig. 81). Moulting continues 

 into adult life in those forms that continue to grow. 



273. General Relation of the Arthropods to Nature. 



The great number of the arthropods insures two things: 

 (i) that in many instances they will prove themselves 

 pests to other organisms, both plant and animal, and (2) 

 that many other animals will depend upon them for food. 

 They are important scavengers and help rid the earth of 

 its decaying matter ; they attack all sorts of living plants 

 and animals; they visit the flowers for pollen and nectar 

 and carry pollen from flower to flower. So close is this 

 adaptation between insects and flowers that some plants 

 are entirely dependent on certain types of insect for the 

 pollination. It is believed by botanists that insects have 

 been one of the most important influences in the develop- 

 ment of the flowering plants as we now have them. 



Insects furnish the chief diet for many birds, lizards, 

 toads, and mammals. The Crustacea are a large part of 

 the food of the fishes, both in fresh and salt water. As 

 would be expected, many insects depend upon other 

 insects for food. 



Insects live through the winter either by hibernation 

 or in the form of winter eggs. Their rapid power of re- 

 production enables them to come quickly to full numbers 

 as spring and its vegetation appears. 



Many arthropods have coloration and form of body 

 that gives them protection by rendering them inconspicu- 

 ous; but it is by no means clear that all the wonderful 

 variety of colors we find among them is of direct use to 

 the possessors. 



