IMPORTATION AND HANDLING OF PAEASITE MATERIAL. 161 



construction have been employed with uniformly good results, and 

 nearly all shipments have been made by mail. All of the parasites 

 have been found amenable to methods of laboratory control, and 

 their reproduction has been undertaken as an economic venture in 

 each instance. Under such circumstances there is no need to import 

 large quantities except for the purpose of discovering other forms of 

 parasites, should they exist. 



HIBERNATING NESTS OF THE BROWN-TAIL MOTH. 



The importation of hibernating nests (PL VII) of the brown-tail 

 moth has been attended with very good success, as a rule, but by no 

 means invariably. If they are sent too early in the winter and sub- 

 jected to long continued high temperature before shipment, or while 

 in transit, the caterpillars will die instead of resuming activity in the 

 spring. 



If sent too late in the spring, exposure to abnormally high temper- 

 atures en route results in premature activity of the caterpillars and 

 they will arrive in bad and sometimes in worthless condition. 



If sent in the middle of the winter they will be very nearly ready 

 to resume activity on receipt, but if again exposed to cold they will 

 become dormant and remain so until about the time when they would 

 normally have become active. This seems not too prejudicial to 

 them, if one is to judge by their activities during the first few weeks 

 after the resumption of activity, but in some subtle manner a change 

 has been wrought, and they do not commonly go through to success- 

 ful pupation. This phenomenon, previously observed with other 

 insects, is discussed at some length in the account of the tachinid 

 Zygoboihria nidicola, which hibernates within the caterpillars, but 

 which does not destroy its host until after it has spun for pupation. 



The failure to rear these caterpillars beyond a certain stage in the 

 spring was at first attributed to some fault in the methods employed, 

 and when it was finally apparent that the fault lay elsewhere there 

 was no longer need to seek to remedy it. The one parasite desired 

 was found to be already introduced and apparently well established 

 as the result of a colonization some three years before. 



The methods for handling the imported nests have varied from 

 season to season in accordance with the habits of the parasites which 

 it was desired to rear from them. These methods will be more fully 

 described in the discussions of the several parasites involved: Ptero- 

 malus egregius, Apanteles lacteicolor, and Zygoboihria nidicola* 



IMMATURE CATERPILLARS OF THE 'BROWN-TAIL MOTH. 



Taken all together, importations of active brown-tail caterpillars 

 (PL VII) in the second to fourth spring stages aggregate a con- 

 siderable number. These importations were undertaken on the 

 . 62188°— Bull. 91—12 11 



