GIPSY MOTH AND BROWN-TAIL MOTH AND THEIE CONTROL. 23 



when the gipsy moth caterpillars are hatching in the spring. It has 

 been proved experimentally that the caterpillars, immediately after 

 hatching, can be blown long distances, and of course such spread is 

 very difficult of prevention. Fortunately the caterpillars must be 

 active or they will not be caught up by the wind, and no activity is 

 possible unless the temperature is high. From this it results that 

 most of the wind spread is toward the north and northeast, so that the 

 danger of spread by wind to territory outside of New England is not 

 serious at present. 



The work of the bureau is being carried on along several distinct 

 lines, namely, experimental work, silvicultural investigations, quaran- 

 tine work, and scouting work. The experimental work is conducted 

 for the purpose of obtaining information which will serve as a basis 

 for better control methods. It includes a thorough study of the food 

 plants of the insects concerned and of the feeding habits of the cater- 

 pillars in their different stages, the rate of increase in the field, the 

 means by which the insects are spread, the introduction and distribu- 

 tion of the foreign parasites and natural enemies of these species, and 

 a study of the wilt disease, which has now become a prominent factor 

 in reducing the infestation in many localities. The last investigation 

 is being carried on cooperatively with the Bussey Institution of 

 Harvard University, and Dr. W. M. Wheeler, who has charge of the 

 economic entomology in that institution, is supervising the technical 

 aspects of the work. A study is also being made, in cooperation with 

 Dr. A. D. Hopkins, who has charge of the Forests Insect Investiga- 

 tions of this bureau, of the secondary insects which attack defoliated 

 trees. 



Silvicultural investigations are being carried on in cooperation 

 with the United States Forest Service. Mr. G. E. Clement has been 

 assigned from that service to this bureau for the purpose of conduct- 

 ing experiments to determine whether better silvicultural practices 

 and improved methods of forest management can be employed as a 

 help in checking the spread of these pests. 



The entire infested area 15,235 square miles occupied by the gipsy 

 moth and 32,420 square miles occupied by the brown-tail moth has 

 been placed under quarantine by the Federal Horticultural Board, 

 and shipments of nursery stock, lumber, cordwood, and other forest 

 products are not permitted to leave the territory unless they have 

 been inspected and are accompanied by a certificate stating that they 

 are free from infestation. This work is designed to prevent the 

 spread of the insects for long distances and is being administered by 

 Mr. D. M. Rogers. 



The scouting work consists in making examinations in the towns 

 outside the infested area and is directed by Mr. L. H. Worthley. This 



