22 BULLETIN 273, U. S. DEPARTMENT OF AGRICULTURE. 



Considering the great numbers of larvae taken in these experiments, 

 there can be no doubt that the wind is almost wholly responsible for 

 the general spread of this insect in New England, notwithstanding 

 the fact that many of the former publications teem with explanations 

 of possible accidental or artificial spread by man and animals. The 

 recent establishment by the Federal Horticultural Board of a quaran- 

 tine on lumber products, Christmas trees, nursery stock, and stone 

 moving from the infested territory, until inspection has been made, 

 has greatly relieved the danger of a general distribution of the gipsy 

 and brown-tail moths over the United States, but the sources of dis- 

 persion of the gipsy moth by the wind can only be lessened by the 

 effectiveness of the parasites and predaceous enemies, together with 

 hand methods of control. To prevent continual spread by the wind 

 into new territory the badly infested areas near the border must be 

 brought under control either by natural enemies, or hand methods, 

 or both. Natural enemies, however, are now playing an important 

 rdle in the control of this insect in the greater area of the inside 

 infested territory. 



The larvae are sufficiently active and allow themselves to be trans- 

 ported by the wind at temperatures of 55° F. and above, and have 

 been caught at wind velocities varying from 2 to 23 miles per hour, 

 although more active spread takes place when the temperature 

 ranges from 65° to 85° F. and when the velocity reaches 8 miles or 

 more per hour. Larva? are removed from their support and carried 

 by sudden gusts of wind, whether they spin or not, when the tempera- 

 ture reaches 50° to 55° F., at which temperatures they often start 

 crawling. 



The records also show that larvse have been caught at times when 

 winds were blowing from all directions except the north — only a very 

 few coming from the east, but the location of the screens along and 

 near the coast materially affected this condition. By far the larger 

 numbers were borne by combinations of the west winds as indicated 

 on the screen at Merrimac, Mass., which was surrounded by a general 

 infestation. 



The general progress of the species since its establishment at 

 Medford, Mass., at the rate of 5 miles per year to the northeast and 

 at the rate of 3 miles per year westward from Providence, R. I., since 

 its first appearance there in 1901 tends to verify the data that have 

 been collected in connection with the screen experiments. 



BIBLIOGRAPHY. 



1893. Wachtl und Kornauth. Beitrage zur Kenntniss der Morphologie, Biologie 



und Pathologie der Nonne (Psilura monacha). In Mittheilungen aus dem 

 forstlichen Versuchsvesen Osterreichs, v. 16, 38 p., 3 pi., 8 fig. 



1894. Cholodkovsky, N. Ueber die sogenannten "Aerophore" der Nonnenraupe. 



In Forst-naturw, v. 3, no. 5, p. 240-243, 1 fig., May. 



