GYPSY AND BROWN-TAIL MOTHS. 45 



from brown-tail nests the winter before. The percentage of the 

 gypsy pupae destroyed was negligible ; but the fact remained that 

 the parasite was on the increase, since exactly the same methods 

 employed in previous years had produced no such results. 



Great curiosity was felt as to the probable character of the 

 results of winter work in the recovery of the hibernating females 

 in the winter nests of brown-tails in the fall of 1909, as this 

 would provide the first opportimity to determine the rate of an- 

 nual increase and of dispersion. The work was begun as soon 

 as practicable, and, while the results are not yet complete, they 

 are more favorable than was at any time anticipated. In brief, 

 the insect is^ now known to be distributed over an area of ap- 

 proximately 3,000 square miles. Every portion of the Com- 

 monwealth north and east of Boston to the New Hampshire line, 

 and as far west and southwest as Leominster, Shirley and Dover, 

 is included in this territory. It is certain to be in New Hamp- 

 shire, but to date none have been received from that State, and 

 the western limits of its distribution have not been determined. 



Everywhere in the area which was not included in its known 

 distribution last year it is about as common as it was in any 

 place the winter before. Within the limits of the territory in 

 which it was known to occur a year ago it has increased at least 

 twenty-five-fold during the year. At this rate, if unchecked, 

 it would be abiindant enough to destroy all of the gypsy and 

 brown-tail pupffi in three years more. Since this, for various 

 reasons, is highly improbable, it is likely that it will reach its 

 maximum effectiveness within the centrally infested areas by 

 that time. Jiidging from the best which it is known to do 

 abroad, this will be the destruction of something like one-fourth 

 of the gypsy and brown-tail pupae. It is not abroad, and cannot 

 be expected to become in America a parasite of as great import- 

 ance as Glvptapanteles or Blepharipa, provided these species 

 become as thoroughlv acclimatized; but it promises to become 

 a very valuable parasite, occupying, as it does, a position in the 

 sequence of parasites which would otherwise be vacant excep 

 for the ineffective Theronia or the less certainly efficient 

 Chalcis. 



