294 JOURNAL OP ECONOMIC ENTOMOLOGY [Vol. 3 



for passing successfully through, the most critical period in its life 

 history, the period of hibernation. That such variation has not yet 

 been found within the species which have but one generation annually 

 is not especially strange. With such forms the host relations and 

 the character of the life processes are fairly definite and restricted, 

 and all of the individuals of the species usually develop to about the 

 same stage by the beginning of winter, whereas in the many-brooded, 

 polyphagous species, there are often at the beginning of the season 

 of hibernation specimens in several stages which must get through 

 the winter as best they can. This we imagine to be the cause of the 

 curious and varied methods of hibernation which have developed in 

 these forms. 



Conclusion. It is quite certain that only a small beginning has 

 been made in the study of the interesting phases of the biology of 

 Tachinid parasites which have been discussed in this short paper. It 

 is hoped that the few data which we have thus far accumulated will 

 be of some interest in themselves; They have in addition a certain 

 practical value, for in the stu^y of any injurious insect a knowledge 

 of its parasitic enemies is desirable. In the case of Tachinids this is 

 sometimes difficult to obtain because failure to rear the parasite to 

 maturity renders its specific determination impossible. This difficulty 

 has been encountered here, more especially on account of a lack of 

 knowledge of the habits of the Tachinids which hibernate in an ad- 

 vanced nymphal stage, which must be provided with conditions as 

 closely approximating the natural as can be devised. Since it is 

 impossible to predict what the habits of a given species may be, all 

 the forms which are met with must be allowed to pupate under the 

 best possible conditions. The method which up to the present has 

 given the most satisfactory results is as follows : Wire screen cylinders 

 are constructed of brass or copper screen, having preferably not less 

 than twenty meshes to the inch. These cylinders may be of varying 

 sizes but it is well to make them not less than six inches in length. 

 They are filled with soil obtained in shaded woodland, a core of earth 

 of the same size as the cylinder being cut out and transferred with as 

 little disarrangement as possible. We have found that with such soil 

 better results are obtained than with loose loam because the innumer- 

 able fine rootlets in the woodland soil prevent the maggot from 

 descending very far before pupation. In loose loam, on the other 

 hand, it may burrow down for a considerable distance before pupa- 

 tion, and the settling of the soil above the puparium during the win- 

 ter may make it difficult or impossible for the fly upon emerging to 

 reach the surface. On this account, too, it is a good plan to pack 



