of the eggs of the brown-tail moth. This is just time enough to 

 insure fertilization and development of the ova. Thus the life cycle 

 of Zygobothria nidicola fits perfectly into that of its host. 



ECONOMIC IMPORTANCE OF THE PARASITE. 



Although Zygobothria nidicola has only one generation a year, and 

 is handicapped by its absolute dependence upon the brown-tail moth, 

 it has become a common species in New England. This means that 

 it is of very great importance in the natural control of the brown-tail 

 moth. Especially in the southern part of the infested area has the 

 parasite proved remarkably effective, despite the fact that it is always 

 the loser when in competition with Apanteles lacteicolor or Meteorus 

 versicolor. In dissections of thousands of hibernating brown-tail 

 moth caterpillars from all sections of New England it has been com- 

 mon to find from 20 to 30 per cent parasitism by Zygobothria. 



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