TACHINID PARASITES OF THE GIPSY MOTH. 217 



been made for cold storage in transit, with the results as mentioned 

 above. 



A very large number of the parasites were secured in this manner, 

 and several thousands of the maggots were allowed to enter the earth 

 in the open in forests infested by the gipsy moth. Others were allowed 

 to pupate in a natural manner in forest soil or in a mixture of garden 

 loam and sand in a variety of containers in the laboratory grounds. 



An examination of these puparia was made from time to time dur- 

 ing the winter and they were found to be uniformly in a much more 

 satisfactory condition than the hibernating puparia had ever before 

 been at that season of the year. So far as could be determined even 

 up to within a few weeks before the emergence of the flies would 

 naturally take place, there was no difference in the condition of the 

 puparia hibernated in different kinds of soil or under slightly different 

 environment. 



Beginning quite early in the spring and continuing through a con- 

 siderable period, flies emerged in very variable proportions from the 

 different lots of puparia. The emergence in a few instances was well 

 up toward 100 per cent. In others it was much lower, and in a few 

 none of the flies completed their transformations. The reasons for 

 these differences were not obvious in every instance, but it was ob- 

 vious that unless conditions are practically identical with those which 

 prevail in the open, the flies will fail to issue in the spring. Moisture 

 is an essential, but is by no means the only essential to success. Nor 

 can failure be attributed to unduly high or low temperatures, or un- 

 natural and abrupt changes in the temperature during the period of 

 hibernation. 



The average percentage of emergence from all of the different lots 

 of pupae has not been as yet accurately calculated, but it was far in 

 excess of any that was secured before, and three colonies which were 

 considered to be satisfactorily large and strong were established in 

 different parts of the infested area. It was not really expected that 

 any of the new generation would be recovered from the field during 

 the course of the first season, and it was therefore considered a par- 

 ticularly good omen when a few were recovered, without difficulty, 

 and under conditions which indicated that dispersion at a quite rapid 

 rate had accompanied a rapid rate of increase. The species has not 

 yet been placed on the list of those considered as thoroughly estab- 

 lished, since it is not certain that it will pass through the complete 

 seasonal cycle in the field, but it is confidently expected that it will 

 five through successfully and that it will be recovered in 1911 in larger 

 numbers. If these expectations are realized there is every reason to 

 believe that it will become a parasite of consequence within the next 

 five years. 



