June, "10] THOMPSON : TACHIXID I'UPATION 283 



NOTES ON THE PUPATION AND HIBERNATION OF 

 TACHINID PARASITES^ 



By W. R. Thojipsox 



The question of the pupation of Taehinid parasites is one which 

 has been found to present itself very frequently to those engaged 

 in the researches in progress at the Gipsy ]\Ioth Parasite Laboratorj', 

 both on account of its biological interest and its practical importance. 

 Very closely connected with the subject of pupation and in some cases 

 bound up with it is that of hibernation. A short resume of our 

 knowledge in regard to these phases of the biology of Tachinids will, 

 it is hoped, be of interest and possibly of some service to those who 

 have encountered the discouraging results which have been often met 

 with here in attempts to breed various species of these parasites 

 through to maturity. 



I am indebted. to Mr. W. F. Fiske for suggesting the preparation 

 of this paper, and for permission to use the data accumulated at the 

 laboratory, for much of which data he is personally responsible. 



Pupation. The general process of pupation among the Tachinidifi 

 is, of course, well known. With very many species it occurs as fol- 

 lows: When the maggot has finished feeding upon the body of its 

 host, and has established itself in surroundings of a suitable nature, 

 it contracts, assuming a regularly ovoid form, the larval skin becomes 

 smooth, gradually infiltrated with a dark pigment and of a hard and 

 resistant character. Histolysis of the larval tissues then sets in and 

 the development of the fully formed adult parasite is accomplished 

 with more or less rapidity. The minute details of the developmental 

 process cannot be considered here but on the other hand there are a 

 number of variations in the process of pupation of a more general 

 and not less interesting character which may be discussed in some 

 detail. The most important of these variations are those which arise 

 from a difference in the reaction of the parasite to the inimical 

 influences to which it is subject in the pupal stage. 



There are two classes of destructive agencies to which Taehinid 

 parasites are subject in the pupal period. These are as follows: (1) 

 Secondary parasitism; (2) Meteorological influences. It is, of course, 

 apparent that most, if not all, Tachinids will be subject in exactly 

 the same degree to secondary parasitism if equally exposed to it. 

 On the contrary, this is not by any means true of their reaction to 

 meteorological influences so that the forms which we have studied are 



^ Occasional contributions from the Gipsy Moth Parasite Laboratory, IV. 



