t82 MAINE AGRICULTURAL EXPERIMENT STATION. 1913. 



LIFE CYCLE OF WOOLLY APHID OF APPLE. 



(Exclusive of root forms.) 



ELM: Primary Host. APPLE: Alternate Host. 



EGGS. 

 (Under bark all winter) 



STEM-MOTHER. 



(first generation in leaf. 

 Apterovis viviparous females). 



NYMPHS. 



f Hibernating young, mi- 

 grating to trunk or 

 branches in early spring) 



SECOND GENERATION. 



(apterous viviparous females 

 in leaf) 



SPRING MIGRANTS Migrate to apple 

 (third generation. Alate viviparous). 



SEVERAI, GENERATIONS. 



Migrate to elm 



APTEROUS OVIPAROUS FEMALES 

 AND APTEROUS MALES. 



FOURTH GENERATION. 



(apterous viviparous females). 



FIFTH GENERATION. 



(apterous viviparous females). 



FALL MIGRANTS. APTEROUS VIVIPAROUS 



(Alate viviparous parthEnogenETic 

 parthenogenetic females, mature in 

 females, mature Aug.-Sept. 

 Aug.-Sept. 

 sexuparae.) 



eggs. 

 (under bark all winter). 



HIBERN.VriNG NYMPHS 



(protected during winter 

 about crown of tree). 



