THE POPULATION OF AN OLD APPLE TREE 303 



in the orchard at almost any time; and by carefully watch- 

 ing, may see them chiseling holes with their stout beaks, 

 and extracting borers from the wood, or caterpillars hidden 

 under the heavy flakes of bark. Their perforations may be 

 found on any old tree, especially in bark and dead bough. 

 Often there are sap-pits to be seen, also, in the fresh green 

 bark of the larger boughs. These are placed in regular trans- 

 verse rows, close together. They are made by sapsuckers, 

 at the time of sap-flow in the early spring (see Chapter 22, 

 page 169). These are made to "bleed" the tree and not to 

 rid it of pests. They are not very harmful, however, for they 

 are made in such a way that they quickly heal in the grow- 

 ing season. The pits are small, and living bark from which 

 new growth may spread is left between the pits. Nature 

 has taught the sapsuckers how to take the sap and soft fiber 

 of the inner bark from the trees without seriously injuring 

 them. The sapsuckers pay for this by eating injurious 

 insects that hide beneath the old and flaky bark of the trunks. 



A few birds are residents in the trees, but many others 

 come and go. Some, like crows and jays, slip in unawares, 

 merely to peck holes in the reddest of the apples on the 

 upper boughs. Others, like cuckoos, come to feed on cater- 

 pillars. There are many mammals that like apples as well 

 as we do ; and some small wild ones make nocturnal visits to 

 the orchard. There are many insects that visit it, in blos- 

 soming time, for nectar or for pollen, as we have seen in 

 Study 30. But the most important part of the population 

 of m the apple tree is the resident population, composed of 

 insects that are wholly dependent on the apple tree for their 

 livelihood. 



These are both beneficial and injurious insects ; and the latter 

 will usually appear to be in excess. There is no part of the 

 tree exempt from the attacks of some of them. On the 

 roots, there are wooly aphids clustering and causing rounded 



