400 Annals Entomological Society of America [Vol. XIII, 



percentage of hatch might be accounted for by the low temper- 

 ature of 1918; however, it is impossible to make a definite state- 

 ment regarding this matter because the evaporating factors 

 previous to the time when the eggs were brought into the labora- 

 tory may have been very different for the two seasons and this 

 may have influenced the percentage of hatch. In other words 

 it is possible that evaporating factors may have been much 

 greater dufing the cold, dry season of 1917-1918 than during 

 the mild wet winter of 1918-1919. This might account for the 

 difference in the percentage of hatch in these experiments 

 which were conducted under similar conditions during the 

 respective season. 



REFERENCES BY AUTHOR. 



1917. Studies on the Morphology and Susceptibility of the Eggs of Aphis avence 

 Fab., Aphis pomi DeG. and Aphis sorbi Kalt. Jour, of Econ. Ent., Vol. 10, 

 pages 556-560. 



1918. Some Studies on the Eggs of Important Apple Plant Lice. New Jersey 

 Agric. Expt. Sta., Bull. 332. 



1919. Response of the Eggs of Aphis avence Fab. and Aphis pomi DeG. to Various 

 Sprays, Particularly Concentrated Lime-sulfur and Substitutes, Season 

 1918-1919. Joum. Econ. Ent., Vol. 12, pages 363-386. 



EXPLANATION OF PLATE XXXI. 



All Figures of the eggs are typical of Aphis avena and Aphis pomi. 



Fig. 1. Dorsal view of a normal dormant egg. 



Fig. 2. Dorsal view of an egg showing an early stage in the usual type of splitting 

 of the outer semi-transparent layer. 



Fig. 3. Dorsal view of an egg showing an advanced stage in the usual type of 

 splitting of the outer semi-transparent layer. 



Fig. 4. Dorsal view of an egg showing an early stage in the emergence of the 

 nymph. Note the egg burster on the head of the nymph along the meson 

 and the cut pigmented inner layer. 



Fig. 5. Map of New Jersey, showing location of orchards where eggs were col- 

 lected for experiments recorded in Table 5. 



Fig. 6. Diagramatic drawing of a moisture control equipment. 



ABBREVIATIONS. 



b. = Egg burster. 



n. = Nymph. 



p. = Inner pigmented layer (chorion). 



t. = Outer semi-transparent layer. 



