i;ivM I,]SAF CURL AND WOOLLY APPLE APHLD. 



247 



I,IFE CYCLE OF WOOLLY APHID OF APPLE. 



ELM: Primary Host. 



EGGS. 

 (Under bark all winter) 



STEM-MOTHER. 



(first generation in leaf curl. 

 Apterous viviparous females). 



SECOND GENERATION. 



(apterous viviparous females 

 in leaf curl). 



APPLE: Alternate Host. 



NYMPHS. 



(From hibernating forms on 

 roots, etc.) migrating to 

 trunk or branches in earljr 

 spring. 



SEVERAL GENERATIONS. 



SPRING MIGRANTS Migrate to apple . 

 (third generation. Alate viviparous). 



FOURTH GENERATION. 



(apterous viviparous females). 



SUMMER GENERATIONS. 

 ON EEM BARK. 



Migrate to elm 



APTEROUS OVIPAROUS FEMALES 

 AND APTEROUS MALES. 



EGGS, 

 (under bark all winter). 



EIETH GENERATION. 



(apterous viviparous females). 



PALL MIGRANTS. APTEROUS VIVIPAROUS 

 PARTHENOGENETIC 



Alate viviparous females, mature in 

 parthenogenetic Sept.-Oct. 

 females, mature 



Sept.-Oct. sexuparae. 



HIBERNATING FORMS 

 ON APPLE ROOT. 



