June, '10] THOMPSON : TACHIXID PUPATION 285 



cent was secured the following spring. That this drying out of the 

 nymph within the puparium, resulting in its death, is in some way 

 correlated with its rapid development to an advanced stage long be- 

 fore it is ready to emerge, there can be but little doubt. Xo reasons for 

 this rapid development can, of course, be given, nor can we definitely 

 state the physiological reasons for the susceptibility of the parasite in 

 this stage to dryness although it seems probable that the greater 

 activity of the organs of the nymph means the requirement and 

 giving off of a great deal of moisture from its body. At all events, 

 an examination of puparia formed under natural conditions in wood- 

 land soil, and dug up in early spring, has disclosed the fact that the 

 nymphs are normally subject to almost semi-aquatic conditions. The 

 spaces between the pupal exuvium and the pupa, and between the 

 pupal exuvium and the wall of the puparium were alike filled with 

 a clear watery liquid. 



The Tachinid larvae seem to be instinctively aware of the danger 

 of pupation under aerial conditions. In spite of the care now taken 

 to send parasitized material from abroad in cold storage, it not infre- 

 quently happens that numbers of the maggots of BlepJmrijM scutel- 

 lata and the two other species mentioned above, emerge from the 

 pup^e of the gipsy moth in the shipping boxes en route. The puparia 

 which these maggots form have been observed to be very often im- 

 perfect, larviform or nearly so, and usually not giving the fly. To 

 determine the cause of the formation of such imperfect puparia and 

 the conditions under which the lan^fe could best pupate, an experi- 

 ment with fresh maggots was undertaken in 1909. A number of these 

 which had just emerged from gipsy moth pupfe were placed upon 

 the surface of the soil in a shaded w^oodland, w^hile others were 

 allowed to pupate under various artificial conditions. The larvas 

 placed upon the soil descended into it very rapidly and formed per- 

 fect puparia in a short time. Little of interest could be deduced from 

 the observations as to the pupation of the maggots under the various 

 artificial conditions until the results thus obtained were compared 

 with those secured by permitting the maggots to pupate in the soil 

 when it at once became clear that in general, pupation is much re- 

 tarded, a great irregularity in the leng-th of the prepupal period 

 is caused and that the maggots sometimes die without pupating, when 

 prevented from entering the earth. So well developed is the instinct 

 of the Tachinid maggots of the first class to seek the earth and bury 

 themselves in it, that if a number of the pupw of the gipsy moth which 

 contain the larvge of Blepharipa be confined in cardboard boxes, the 

 maggots upon emerging from the pup^e will at once burrow down to 



