TACHINID PARASITES OF THE GIPSY MOTH. , 211 



earth for a distance of several inches in quest of puparia which have 

 been buried therein, and since they can pass through well-nigh invis- 

 ible cracks and are in possession of an acute maternal instinct, they 

 are able to enter receptacles of all sorts by means of openings far too 

 small to permit the passage of any other among the secondary para- 

 sites which have been studied, not excepting those from the gipsy- 

 moth eggs. 



Having located their prey, oviposition follows, the eggs are de- 

 posited upon the surface of the nymphs in an irregular circle sur- 

 rounding a wound made by the ovipositor. They are very small but 

 appear to swell somewhat before hatching, and if the puparium is 

 broken open so that they are freely exposed to the air, they will not 

 hatch at all. Contrary to expectations the larvae and their mode of 

 life presented nothing abnormal. The number of larvae or pupae 

 which had been found in the hibernated Blepharipa in the spring of 

 1907 was so extraordinarily large in comparison to the size of the 

 mother insect that it was considered likely that some form of polyem- 

 br}^ony or paedogenesis would be found upon further study. 



Becoming full fed, they will pupate immediately if the temperature 

 is uniformly high, but will hibernate if it is allowed to fall below a 

 point which was not determined. As soon as pupation has taken 

 place the sexes are easily separable, through the absence of wings and 

 eyes in the males. The male pupae develop much more rapidly than 

 the females and the adults issue in advance of their mates. They are 

 invariably in the great minority, and their relative numerical strength 

 is still further reduced through the terrific duels which follow their 

 emergence. Notwithstanding their physical defects in the matter of 

 sight and powers of flight, their seeming weakness otherwise, and 

 their small size, even when compared to their mates, they possess a 

 courage and a vigor that is most surprising. In the instance of a 

 colony which had been removed, from the puparium in which it was 

 reared through its early stages, to a small glass cell, the several males 

 which issued well in advance of the females engaged forthwith in con- 

 flict, in the course of which a considerable number was killed. The 

 survivors of this Lilliputian battle royal calmly awaited the issu- 

 ance of the members of their harems and proceeded to mate with one 

 and all with an ardor which seemed to know no limit. 



Mr. Smith also conducted an experiment in parthenogenesis, the 

 results of which were and remain unique in the annals of the labora- 

 tory. As in every other instance in which an attempt has been made 

 to secure parthenogenetic reproduction with the hymenopterous para- 

 sites, it was successful, but in this case to a limited degree only, in 

 that the females positively refused to deposit more eggs than they 

 would normally have produced males had they been properly fertilized. 

 Instead of depositing sufficient to provide for the complete consump- 



