308 INSECTS AFFECTING VEGETATION 



usually made its way to one of the large branches, leaving behind it 

 one or two that will be almost certainly broken by the winter winds. 



During the second summer growth is rapid and the larvae at- 

 tain a length of two inches or more. On smaller trees they some- 

 times get into the trunk itself and may completely girdle it; or they 

 may remain in the branches, or, in fact, work in almost any con- 

 ceivable way, changing their location two or three times during 

 the summer. At the end of this growing season they have reached 

 their full size and, early in the spring following, work close to the 

 surface and form pupse, which, when the adults are ready to develop, 

 wriggle their way out so that fully half projects beyond the bark 

 when the moths emerge. The moths do not feed. The caterpillars 

 do not feed upon the surface except for a short time, when they 

 change their quarters and start at a new place. There is no chance 

 of reaching the moths through poisonous applications and prac- 

 tically no chance of reaching the larvae by means of insecticides. 



Thus far the insect has been confined to the cities, and while 

 occasionally in the outskirts specimens are found in trees, it is the 

 exception rather than the rule and practically no injury is done in 

 orchards or to the trees of smaller towns and villages. The larger 

 the city the greater the injury, and the reason for that seems to be 

 that in such places no birds, except English sparrows, are able to 

 maintain themselves. Wherever this sparrow' is completely in pos- 

 session the insect is no longer to be feared. 



Active measures are possible in one direction only. Every 

 badly infested tree should be cut down and burnt, as its death is a 

 mere matter of time at the best. Trees infested toward the tips only 

 should be cut back in winter and the cuttings should be burnt. The 

 openings to the burrows made by the larvae are easily seen by the 

 trained eye, especially during early summer, when the larva forces 

 great strings of partly digested wood through the opening by which 

 it entered. Where these burrows are in the trunks of valuable trees 

 or shrubs, or in branches that cannot be easily spared, a few drops of 

 bisulphide of carbon may be injected by means of an oil-can or a 

 small syringe, and the opening closed with a lump of putty. The 

 vapor of the bisulphide will penetrate the full length of the tunnel 

 and kill the larva, wherever it may be, without injury to the tree. 

 Most of this work can be done during the winter. During the sum- 

 mer the trees should be kept under constant supervision, and wher- 

 ever signs of borers are noticed the infested wood should be cut out, 

 or the borer should be destroyed by means of the bisulphide of 

 carbon. 



There are undoubtedly natural enemies other than birds that 

 tend to keep this borer in check. If the work of these natural ene- 

 mies is supplemented by systematic work on the part of those in 

 charge of the trees, a great lessening of injury will result. If in the 

 public parks and squares in the cities other birds than sparrows could 

 be introduced and protected, the work w r ould be much simplified. 



The Maple Tree Sesiid. This is another caterpillar borer, 

 found in soft maples more generally. It makes round holes, not 



