INTERRELATIONS OF PLANTS AND ANIMALS 29 



On any bright warm day in the fall we will find insects swarming 

 everywhere in any vacant lot or the less cultivated parts of a city 

 park. Grasshoppers, butterflies alighting now and then on the 

 flowers, brightly marked hornets, bees busily working over the 

 purple asters or golden rod, and many other forms hidden away 

 on the leaves or stems of plants may be seen. If we were to select 

 for observation some partially decayed tree, we would find it also 

 inhabited. Beetles would be found boring through its bark and 

 wood, while caterpillars (the young stages of butterflies or moths) 

 are feeding on its leaves or building homes in its branches. Every- 

 where above, on, and under ground may be noticed small forms of 

 life, many of them insects. Let us first see how we would go to 

 work to identify some of the common forms we would be likely to 

 find on plants. Then a little later we will find out what they are 

 doing on these plants. 



How to tell an Insect. — A bee is a good example of the group 

 of animals we call insects. If we examine its body carefully, we 

 notice that it has three regions, a 

 front part or head, a middle part 

 called the thorax, and a hind portion, 

 jointed and hairy, the abdomen. We 

 cannot escape noting the fact that this 

 insect has wings with which it flies 

 and that it also has legs. The three 

 pairs of legs, which are jointed and 

 provided with tiny hooks at the end, 

 are attached to the thorax. Two 

 pairs of delicate wings are attached 

 to the upper or dorsal side of the 

 thorax. The thorax and indeed the 

 entire body, is covered with a hard 

 shell of material similar to a cow's 

 horn, there being no skeleton inside for 

 the attachment of muscles. If we 

 carefully watch the abdomen of a 



living bee, we notice it move up and down quite regularly. The 

 animal is breathing through tiny breathing holes called spiracles. 



An insect viewed from the side. 

 Notice the head, thorax, and 

 abdomen. What other char- 

 acters do you find ? 



