16 N.S. ENTOMOLOGICAL SOCIETY. 



The Rosy Apple Aphis. 



(Aphis sorbi Kali). 



This aphis gets its name from the fact that the wingless summer 

 forms have a rosy or pinkish tinge. The stem mothers that hatch from 

 the egg vary greatly in color,but are usually of a somewhat blueish shade 

 with a tinge of green. The hinder part of the body is tinged with pink. The 

 young of these forms are pinkish, and like the stem mothers are covered 

 with a whitish powder. The third stage develop into brown or black 

 spring migrants. The fall migrants resemble the spring migrants very 

 closely in appearance, and except by a very careful examination, the 

 migrants cannot be distinguished from the males. The oviparous are 

 wingless, much smaller than the viviparous females and yellowish in col- 

 or. 



Life History. The eggs of the Rosy Aphis which resemble those of the 

 green aphis in appearance, are laid upon the twigs or even upon the trunk 

 of the tree. They are not so noticeable as those of the green aphis being 

 more scattered and often concealed under a bud scale or elsewhere. They 

 hatch at about the same period as does the the green apple aphis and the 

 stem mothers on reaching maturity, begin to produce young very rapidly. 

 The five stem mothers which we reared produced 236, 187, 110, 274, and 

 78 young respectively, or an average number of 177 young, while 37 in- 

 dividuals of the second generation produced an average of 106.51 young 

 each. 



The third generation females develop into spring migrants that fly 

 to plantains (Plantago major or Plantago lanceolata) and there deposit 

 young. From two to five generations are spent on the plantains in Nova 

 Scotia, the last generation developing into winged fall migrants that re- 

 turn to the apple and there give birth to sexual males or females, which 

 pair in the ordinary way, after which the female deposits her eggs. As 

 in the case of the green aphis the female sex predominates in numbers 

 and a single male serves several females. 



Under certain conditions a certain proportion of the species may 

 not develop migrants, but instead remain upon the apple throughout the 

 season. Crowding of specimens upon a single plant stimulates the pro- 

 duction of winged forms. Where there is plenty of room, however, wing- 

 ed forms fail to develop. Thus in the laboratory, where only one aphis 

 was kept on a plant, with one exception, no spring migrants were pro- 

 duced. Where a large number are placed on a single plant, all developed 

 into spring migrants in the 3rd generation. 



Strange to say most of the specimens kept on separate plants be- 

 came winged in the 7th generation. Most of these died, but some when 

 transferred to plantains began to give birth to young. 



