290 .JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 3 



phase of the question has been discussed already under "Pupation." 



Another group of Tachinid parasites, which probably have but one 

 generation annually, are those which pass the winter within the body 

 of the living host. Of these we have observed but a few examples, but 

 they are of exceptional interest. One of these forms is Zygobothria 

 nidicola Towns., which as a parasite of the brown-tail moth, passes 

 the winter as a first stage maggot in the hibernating larva of its host. 

 It is evident that in this case the factor controlling the stage in which 

 the Tachinid shall hibernate is the very small size of the over-winter- 

 ing larva of the brown-tail. Were the parasite to feed only until it 

 had reached the second stage, the death of the host would almost cer- 

 tainly result immediately, or it would be so weakened that it would 

 perish during the winter, in which cases the Tachinid would also 

 succumb. The larva therefore remains quiescent within the body of 

 the host until the latter has fed for some time in the spring. 



Another instance of hibernation within the living host has been 

 found to occur in the case of an undetermined Tachinid parasite of 

 Euchaetias egle. The development of this parasite, w^hich we have 

 found in very small caterpillars, is very slow, and the maggot passes 

 the winter in the second stage within the hibernating pupa of the host, 

 its larval life cycle occupying over eight months. In the spring it 

 completes its larval development and emerges to pupate. It seems 

 evident that this adjustment of the life cycle of the parasite to cor- 

 respond with that of the host must be of advantage to it, otherwise 

 it would complete its development within the host in the autumn and 

 pass the winter in the pupal stage. 



As has been indicated above, it seems probable that both of these 

 species are single-brooded as the larval stage is of such long duration, 

 but it is impossible to say so definitely. In the present state of our 

 knowledge in regard to these subjects it is dangerous to draw many 

 deductions. It will, in fact, be rather surprising if subsequent dis- 

 coveries do not upset some of the generalizations which we have 

 ventured to make. 



One of the most interesting modes of hibernation which we have 

 yet discovered has been found with some forms which pass the winter 

 as third stage larvse within the dry and otherwise empty skin of the 

 host, emerging therefrom and pupating in the spring. This method 

 of hibernation we have so far observed only with two undetermined 

 species, one a parasite of Datana sp., the other infesting a European 

 caterpillar, which is possibly Cnethocampa processionea. The condi- 

 tion of the hibernating larva3 is characteristic and worthy of remark. 

 They are of a golden yellow color, this color being very probably due 



