SUMMARY OF INSECT CONDITIONS DURING 1921. 51 



favorite food plants, is not commonly grown : the white oak, which 

 was a favorite food plant during the period of the insect's greatest 

 abundance in eastern Massachusetts and southern Xew Hampshire, 

 is rarely met with in the northern sections of Xew Hampshire and 

 Maine, inland from the sea coast ; nor is the apple as common a tree 

 in the latter sections as in the southern parts of Xew England. The 

 lessened number of these favorite food plants, however, is not the 

 only cause of the species failing to survive in the northern sections 

 of Xew England. The adults sometimes move in tremendous flights, 

 long distances from their origin, and after depositing their eggs 

 their larvae develop to the hibernaculum stage, where they are killed 

 by the extremely low temperatures typical of these sections. Winter 

 killing of the larva? in their hibernacula is prevalent every winter 

 in the sections mentioned above, and more or less so during severe 

 winters in all sections of Xew England which are distant from 

 the sea coast. 



Introduced parasites and the native fungus Entomophthora 

 aulicae, especially the former, are tremendous factors in the control 

 of this species over the infested area. 



WASHINGTON I GOVERNMENT PRINTING OFFICE : 1922 



