THE GIPSY MOTH ON CRANBEREY BOGS. 3 



cranberry bogs become infested with gipsy moth larvae. In view 

 of the fact that cranberry foliage is not a very favored food which 

 gipsy moth larvse seek by choice, and as the bog does not offer 

 favorable conditions for reproduction of the moths from year to 

 year, it is obvious that wind dispersion is an important, if not the 

 most important, factor to be considered in studying the infestation 

 of bogs. 



WIND DISPERSION OF GIPSY MOTH LARV^. 



HISTORY. 



The first investigations of wind dispersion of the first-stage gipsy 

 moth larvae were made in 1910 b}- A. F. Burgess and recorded in Bul- 

 letin No. 119 of the Bureau of Entomology. These investigations 

 established the fact that the young gipsy moth caterpillars, soon after 

 they emerged from the egg, were carried considerable distances by 

 the wind. This was the first indisputable explanation of the origin 

 of isolated infestations in woodlands, as well as those that were 

 frequently located in territory outside of the known infested area. 

 The spread of this insect in a northeasterly direction year by year, 

 it v/as found, was due to the fact that the wind usuall}^ blows from 

 the southwest at the time when the young caterpillars first reach the 

 tops of the trees. 



In 1913-14 C. W. Collins carried on a series of experiments to de- 

 termine the distance young caterpillars would be carried by the wind. 

 The results of these experiments are recorded in Bulletin No. 273 of 

 the U. S. Department of Agriculture, in which it is shown that under 

 favorable conditions the small caterpillars were carried 13^ miles. 

 Later experiments have demonstrated that they may be carried 20 

 miles, and it is probable that under the most favorable conditions the 

 spread is even greater. 



SELECTION OF A BOG FOR EXPERIMENTAL PURPOSES. 



Several bogs in the cranberry region were examined and the one that 

 seemed best suited for the experiments was in the northern part of 

 Carver, Plymouth County, Mass. This bog was approximately oval in 

 form, about 3,600 feet long and 2,000 feet across at its widest part. The 

 bordering uplands were typical of the region, consisting of eleva- 

 tions, from 10 to 50 feet in height, well wooded with pine, oak, birch, 

 and some maple, with a few stands made up mainly of oak and birch. 

 Egg clusters of the gipsy moth were found in these bordering wood- 

 lands, and were particularly plentiful on the western border. Some 

 sections of this area were already in bog, one portion was in process 

 of reconstruction, and the remainder was the bed of a pond that had 

 recently been drained for the purpose of converting the whole area 

 into one large cranberry bog. (PI. I, Fig. 2.) 



