2 THE GIPSY MOTH AS A FOREST INSECT. 



As an orchard insect it is not infrequently eclipsed by the American 

 tent caterpillar. Even the forests have suffered less than early pre- 

 dictions would have led one to expect. It is certain that the situation 

 has become measurably improved within recent ^^ears. 



CAUSES OF THE IMPROVED CONDITIONS. 



This obvious improvement is in part only apparent and in part 

 very real and due to a variety of causes. The apparent amelioration 

 is due to the fact that the gipsy moth is at present most active in a 

 belt of towns beyond the limits of the densely populated metropolitan 

 area. Were Boston's parks again to be infested as formerly; were the 

 forests in the Middlesex Fells, for example, to be defohated, a wave 

 of remonstrance would arise which might be heard halfway across 

 the continent. But a thousand acres of forest in the sparsely popu- 

 lated and financially poor towns 30 to 50 miles away may be repeatedly 

 defoliated and ultimately destroyed without creating more than a 

 ripple in comparison. And this latter is precisely what is taking 

 place at the present time. It will be necessary to wait until in its 

 slow progress the gipsy moth invades another great metropolitan 

 area before popular interest will be aroused to an extent comparable 

 to that existing in Massachusetts a few years ago. 



The redl amelioration so noticeable in the metropolitan district, and 

 distinctly in evidence everywhere, is due to at least four main causes: 

 (1) The perfection and standardization of the methods for artificial 

 repression; (2) the death of a large proportion of the more susceptible 

 trees or their removal from the infested woodlands; (3) the importa- 

 tion of parasitic and predatoiy insect enemies; and (4) the develop- 

 ment of the ''wilt" disease. 



As it is intended at this time to consider the gipsy moth strictly as 

 a forest insect no mention need be made of the methods for artificially 

 suppressing it. On account of their expense these methods can not 

 be used in forests other than those which it is desired to protect for 

 aesthetic and sentimental reasons. 



RESULTS OF PARASITE IMPORTATION. 



There are about 30 species of insect enemies of the gipsy moth which 

 appear to be of importance in checking its increase in Europe and 

 Japan. All of the promising species have been imported and colo- 

 nized under more or less satisfactory conditions in America. Not all 

 have successfully accommodated themselves to their new environment. 

 About one-third of the total appear to have done so and to be steadily 

 increasing in efficiency in accordance with their powers of multipli- 

 cation and dispersion. 



It was hoped that more of them would acclimatize themselves; it 

 was feared that the number might be less. On the whole, the results 



