October, '19] PETERSON: APHID EGGS 365 



this is the only species present in the orchard a great amount of injury 

 will not take place. The only way to be sure A. sorbi and A. pomi 

 are not present is to make a careful determination of the adult 

 forms during the fall of the year. Observations made at this time 

 will give one a fair estimate as to what species will be troublesome 

 in the spring. Careful examinations of numerous orchards through- 

 out the state for three years during October, November and December, 

 has shown that where aphides are present 75 percent or more of infested 

 orchards possess some or many adults of A, sorbi. The black shiny 

 eggs of A. sorbi and A. avence resemble each other and they are de- 

 posited by the female in similar situations (usually on the second year 

 wood), consequently it is impossible to distinguish the two species 

 during the dormant season. The first nymphs to hatch in the spring 

 are A. avence (usually at the time when the fruit buds first show green) 

 and these may be distinguished from A. sorbi and A, pomi which hatch 

 10 to 14 days after A. avence. In New Jersey the eggs of A. sorbi and 

 A. pomi hatch too late to safely or satisfactorily apply a delayed dor- 

 mant spray of lime-sulfur and nicotine during or after the eggs of these 

 species have hatched. Consequently it is not advisable to wait until 

 the hatching period of A. sorbi and A. pomi has passed in order to 

 determine the presence of the injurious species and then attempt to 

 obtain a satisfactory control. 



The above facts concerning plant lice eggs on apple trees leads to 

 the conclusion that it is highly advisable to apply a delayed dormant 

 spray if aphid eggs are found on the trees, during the dormant season. 

 If one has made a careful examination of the adult forms during Octo- 

 ber, November and December, and is certain that A. avence is the only 

 species present, it might be safe to ignore the presence of the aphid 

 eggs on apple trees. 



Morphology and Behavior of the Eggs 



Observations on the morphology and the behavior of aphid eggs 

 were repeated this past season and it was again observed that the 

 eggs of A. avence and A. pomi (for observations on A. sorbi see N. J. 

 Agr. Expt. Sta. Bull. 332) show two distinct layers in the egg shell, an 

 outer, semi-transparent layer which is soft and glutinous when the 

 egg is deposited, and an inner soft elastic membraneous black layer. 

 After the egg is dc^positod the outer layer hardens and becomes some- 

 what tough and impervious upon long exposure to wcatlier. A third 

 layer or skin may be seen about the nymph when it emerges. This 

 is an embryonic membrane or the first exuvium. It is shed by A. 

 avence when the nymph is half-way out of the shell, while with A. 

 pomi it is not shed until the nymph is practically free from the entire 



