22 BULLETIiSr 1028, U. S. DEPARTMENT OF AGEICULTURE. 



Often the j^arasite is recovered the year following colonization. 

 A. melanoscelus has been recovered from all but one of the colonies 

 liberated previous to 1918. It has been recovered from half of the 

 colonies put out in 1918 and from both of the colonies liberated in 

 1919. Eecoveries of the parasite were made late in the summer of 

 1920 in a few of the towns which were colonized during June of that 

 year. 



DISPERSION. 



The inner black line on the map (PL IV) shows the present known 

 distribution of the parasite in New England, it having been recovered 

 from practically every town within this line. It is probable that in 

 some cases A. melanoscelus has spread beyond the line indicated, for 

 many of the towns just outside of the dispersion line have not been 

 scouted. 



It is rather difficult to determine the exact distance the parasite 

 will spread in a year, for when the parasite is scarce its recovery is 

 largely a matter of chance. The number of host larvae which it is 

 practical to collect in an endeavor to rear the parasite for disper- 

 sion records is infinitesimal when compared with the larvae present 

 in a town. Scouting for the cocoons is more satisfactory, but this 

 is not infallible, and the fact that a town may have been scouted and 

 no cocoons found does not prove that the parasite is not present. 



The recovery records show that the greatest spread of this species 

 has been to the north and northeast, similar to the dispersion of the 

 gipsy and brown-tail moths. The data obtained indicate a spread 

 of about 25 miles a year in this direction. During the summer of 

 1918 there were two recoveries made which because of their loca- 

 tions are of special interest. One of these recoveries was made at 

 Provincetown, which is 25 miles northeast of Harwich, where the 

 nearest colony of A. melanoscelus was liberated in 1915. The other 

 recovery was made on the island of Nantucket, which is 25 miles 

 south of the Harwich colony. In 1915 a colony of A. melanoscelus 

 was liberated in Middleboro, about 33 miles southwest of Prov- 

 incetown. The colonies at Harwich and Middleboro were the only 

 ones that had been liberated in that part of the State. These recov- 

 ery records can not be taken as absolute proof of a flight of 25 miles 

 for the insect, as it is possible that cocoons of the parasite were taken 

 to Provincetown and Nantucket on cordwood or other material. This 

 does not seem likely, however, for the parasite was not recovered from 

 any of the other towns in southeastern Massachusetts until 1919. The 

 number of cocoons taken at Provincetown and Nantucket in 1918 

 indicated that the j^arasite had been present in both places for 1 year 

 at least. 



