IMPORTATION" AND HANDLING OF PARASITE MATERIAL. 159 



possible. The remainder were placed in small tube cages, and taken 

 to the field where they were to be liberated. An attendant counted 

 the number of flies issuing, and watched for secondary parasites. 

 Since no secondary parasites issued in the summer from pup aria 

 secured in this manner, in 1910 the puparia were merely, placed in 

 cages which were taken to the colony site and left unattended until 

 the flies had ceased to issue. 



After the adults of the summer-issuing forms have all ceased to 

 emerge, the sound puparia are more or less carefully sorted. Those 

 supposed to be Parasetigena segregata, indistinguishable externally 

 from dead Tricholyga or Tachina, are buried in damp earth for the 

 winter. Mr. J. D. To thill, one of the assistants at the laboratory, 

 devised an ingenious method for separating the puparia containing 

 the healthy pupae of Parasetigena from those containing dead Tachina 

 or Tricholyga, by holding them so that they were viewed against a 

 narrow beam of very strong light. The method was not infallible, 

 but served its purpose fairly well, and was the first of many which 

 had been experimented with which was at all successful. 



The living caterpillars removed from the boxes have been placed 

 in cages or trays and fed, but only an insignificant proportion of them 

 has ever lived long enough to be killed by the parasites which many 

 of them have contained. Large numbers of them have been dissected 

 for the purpose of determining the proportions parasitized. 



The dead caterpillars not infrequently contain the puparia of 

 Tricholyga, when this parasite happens to be common in the locality 

 from which the shipment originated. Under such circumstances 

 they are placed in tube cages for the emergence of the flies. If 

 Tricholyga is not present in the boxes in the form of free puparia the 

 dead caterpillars may as well be discarded, since it is only very 

 rarely that any other tachinid pupates in this manner. 



Pupae, both living and dead, nearly always contain a considerable 

 number of the larvae of BlepJiaripa scutettata. They are, therefore, 

 placed over damp earth in order that the larvae may pupate under 

 natural conditions. Other tachinids may occur in the pupa, but 

 never in anything but insignificant numbers. 



GIPSY-MOTH PUP^E. 



It would seem as though it ought to be an easy matter to import 

 the pupae (PI. VI) of the gipsy moth in good condition, but for 

 reasons which are not altogether clear in every instance the vast 

 majority of the importations of pupae have been worthless, or worse 

 than worthless, since the handling of worthless material involves an 

 additional waste of labor. Too often the cause of failure is directly 

 and obviously the result of careless packing, and the number of lots 

 of pupae which have been received packed with the care which is 



