Some Studies on the Influence of Environmental Factors on the Hatching of the Eggs of Aphis Avenæ Fabricius and Aphis Pomi DeGeer.*

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Abstract
The eggs of Aphis avenue Fabricius1 and Aphis pomi DeGeer have two distinct layers in the egg shell (Figures 1 to 4). The outer layer, when the eggs are first deposited, is transparent, soft and glutinous, but it soon hardens upon exposure to weather conditions and becomes semi-transparent, toughened, dry and decidedly impervious to water. The inner layer is a soft, elastic, black membrane and decidedly pervious to water. The outer layer usually splits (Figures 2 and 3) along the dorso-mesal line a number of days before the nymph emerges. The above structure and splitting of the outer layer is also characteristic of the eggs of other species of plant lice; a species of Lachnus, which deposits its eggs on the needles of whitepine, another aphid which deposits its eggs about the buds of weeping willow and at least one species of aphid which deposits its eggs in ant nests. I am indebted to Mr. J. L. King for furnishing me with eggs from an ant nest.

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