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



To secure further information, the writer, under the direction of 

 Mr. A. F. Burgess, commenced a series of experiments in the spring 

 of 1913 and continued them throughout the following year. 1 



PREVIOUS INVESTIGATIONS ON DISPERSION OF THE GIPSY MOTH. 



Many investigations of various sources of spread of this insect were 

 conducted during the early nineties by Forbush and Fernald and 

 published by the Massachusetts State Board of Agriculture in 1896. 

 It was found that frequent teaming in and out of the original infested 

 areas (Medford, Boston, and towns closely surrounding) by vehicles 

 transporting larvae that dropped from infested shade and roadside 

 trees was largely responsible for the general local spread during those 

 years. It was also suggested that the larvae were occasionally trans- 

 ported by the wind to distances of perhaps 100 yards, but no further 

 observations were made at that time to substantiate this theory. 

 Numerous ways and means of local spread, such as by birds, animals, 

 and man, are treated in this valuable report. 



In the spring of 1910 Mr. A. F. Burgess began a series of experiments 

 on dispersion of the gipsy moth the account of which is published as 

 Bulletin 119 of the Bureau of Entomology. A few small experiments 

 were made in the laboratory by releasing silk-suspended first-stage 

 gipsy-moth larvae in front of an electric fan, and it was found that 

 they soared to a distance of 20 to 30 feet in the air before falling. 

 This led to more extensive experiments conducted under out-of-door 

 conditions. Screens constructed of poultry wire and covered with 

 tanglefoot were stationed at given distances from souroes of infesta- 

 tion and watched for catches of larvae. On a small screen stationed 

 on the marshes near Lynn, Mass., newly hatched larvae were caught 

 that had been carried 1,833 feet by a west wind at a velocity of 7 to 

 19 miles per hour. 



Numerous records were compiled to show the relation of tempera- 

 ture, wind velocity, and wind direction to the general trend of spread 

 as it has progressed from the original center, Medford, Mass. It was 

 clearly demonstrated that the prevalent southwest winds following 

 the hatching period of the eggs each year has resulted in the more 

 rapid dispersion of the moth to the northeast than in any other direc= 

 tion. Large woodland areas were scouted in various towns, the 

 data of which were compiled and show the extent to which the wind 

 is responsible for the remote and numerous colonies located. The 

 automobile is also included in this report, as a very important factor 

 in carrying the caterpillars both locally and for long distances. 



1 The writer is indebted to Mr. L. H. Worthley and Dr. J. W. Chapman for cooperation and helpful 

 suggestions; to Messrs. C. E. Hood, F. W. Graham, and Harry Blaisdell for the collection of field data; 

 to Mr. H. A. Preston for the preparation of photographic illustrations, and to others of the laboratory 

 force who contributed in various ways. 



