166 PARASITES OP GIPSY AND BROWN-TAIL MOTHS. 



to be concluded in considerably less than one week after the spinning 

 of the cocoon if the weather is hot, and even, under the best of con- 

 ditions which can be devised for keeping them alive the mortality is 

 heavy. Even in the ordinary temperature of a steamship's cold 

 room development continues. 



TACHINID PUPARIA. 



The importation of tachinid puparia is by no means so simple as 

 the importation of Apanteles cocoons, but at the same time it is easy 

 as compared with the difficulties attending the importation of live 

 gipsy-moth caterpillars from which to rear these puparia in America. 



In all, quite large numbers have been received from both Europe 

 and Japan. A variety of methods has been tested in the hope of hit- 

 ting upon one that would be applicable for the purpose. Shipping 

 in damp earth was early attempted, and seems to be the very first 

 method which suggests itself to anyone wishing to ship a quantity 

 of them, but of all ways it is very nearly the worst. It would prob- 

 ably be the best, if the larvae could be allowed to enter the earth 

 naturally and if they were left there wholly undisturbed throughout 

 the time they were in transit, but mingled with damp earth and 

 placed in a box to be sent by mail or express, disaster is pretty sure 

 to result. Cotton has also been used several times, and it is usually 

 as bad and sometimes worse. With the exception of excelsior, cot- 

 ton is about the worst packing for living insects that has come under 

 observation at the laboratory, although gritty moss, of a sort which 

 dries brittle, is also bad. Presumably there are other worse sub- 

 stances, but they have not been discovered at first hand. 



Probably the best packing material is slightly damp and preferably 

 living sphagnum moss. The live moss retains its moisture in a man- 

 ner wholly different from the moss which has been killed, dried, and 

 subsequently dampened. Test shipments, which were sent to France 

 and back without being opened, returned to the laboratory in good 

 and almost unaltered condition, in the case of those which were 

 inclosed in tight boxes. Even when fully exposed to the air the liv- 

 ing moss seems to dry much more slowly and to hold its moisture 

 more naturally. Sphagnum possesses the great additional advan- 

 tage of being much softer when dry than most other kinds of moss. 



One disadvantage attending the shipment of puparia, no matter 

 how they are packed, is that of secondary parasites. A single colony 

 of Dibrachys, issuing en route from one of a lot of puparia, will result 

 in the parasitism of a large proportion of the remainder. This 

 might possibly be prevented by packing in sand or earth, but this 

 appears to be about the only advantage possessed by that method. 



The puparia of certain tachinids must be kept damp, but this is not 

 at all necessary in the case of all. Methods of packing and shipment 



