384 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 3 



found to group themselves into two classes according to the effect 

 which exposure to the last-named conditions has upon them. These 

 classes may be described as follows: 



(1). Those which habitually and of necessity enter the earth to 

 pupate. (These being the forms upon which meteorological condi- 

 tions exert a great influence.) 



(2). Those which do not habitually and of necessity enter the 

 earth to pupate, or do not do so in order to avoid the influences which 

 affect the parasites of the first class. 



It must be admitted that by characterizing the two divisions in this 

 manner the difference between them does not appear to be very 

 strongly marked. This is due in part to a very considerable varia- 

 tion in the habits of the parasites of the second class and some ex- 

 planation is needed to make clear the compact nature of each group. 



Whether or no the pupation of the Tachinid larva in the soil is of 

 vital importance to it seems to be determined largely by, first, the 

 duration of the pupal period and, second, the condition of the hiber- 

 nating nymph within the puparium. In respect to the first men- 

 tioned factor it may be stated that while with all of the parasites of 

 the first class the pupal period is of long duration this is sometimes 

 also the case with those of the second class. The second factor is the 

 important one as we shall now try to make clear. 



Pupation of Tachinids of the first class. The pupation of these 

 forms is characterized by the rapidity of the development of the pupa 

 up to a certain point. Histolysis of the larval tissues and the develop- 

 ment of the nymph to the stage where the external structures, such 

 as the eyes, antenna?, macrochffitffi, legs, wings and other appendages 

 are as perfectly developed as they are in the i\y on the point of issuing 

 from the puparium, is accomplished frequently within thirty days 

 after the formation of the puparium, and always long before the 

 winter sets in. Among the forms which develop in the manner 

 described may be mentioned BlepJiaripa scutellata Rdi. (R. D.), 

 Crossocosmia sericarice Rdi., and Parasetigena segregata Rdi., all 

 important parasites of the gipsy moth. In the condition described 

 the Tachinids are peculiarly susceptible to meteorological influences, 

 especially in so far as these induce the drying up of the nymph within 

 the puparium. From a large number of the puparia of Blepharipa 

 ■scutellata and Crossocosmia sericaricB received at the laboratory in 

 1908 which were forced to pupate out of earth on account of the con- 

 ditions under which the parasitized pupee of the gipsy moth were 

 shipped from Europe and Japan, and which were kept during the 

 winter in cold but dry conditions, an issuance of less than one per 



