IMPORTATION AND HANDLING OF PARASITE 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 
Zygobothria 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 Zygobothria nidieola. 
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 
95677 °—Bull. 91—11 11 
